E Brake Cable Fun (the wholesome kind)

Good Evening Ladies and Mogwai,
Hailing from the great state of Maine (where we salt the roads heavily enough that when it snows the lobsters can come ashore to breed), is a wonderful 2005 Prius II with a bit of an underbelly issue. I'm getting myself set up for fluid filming from here on out, but need to deal with a few rust issues before I even get to preventative maintenance.

Deets:
2005 Prius
160k miles
No major issues (yet)
Two owners - one Vermont and myself in Maine
Issues: rust, rockers, e brakes, muffler, rear drums overhaul, brake bleed (likely through Toyota)

Does anyone have any experience replacing the e-brake cables that run from just above the exhaust resonator down to each of the rear drum brakes, and possibly a few good ideas for drilling/tapping new holes for some rusted-away brackets and bolts? Specifically, does anyone know what the 10mm bolts are so I can look for replacements, and does anyone have any experience drilling and tapping new mounting holes through the frame or floor pan?

Right off the bat, I realized that all the bolts and brackets that hold the e brake line/cable in place are either going to crumble away when I turn the bolts, or snap. No penetrating lube or heat is going to solve this one. I'm going to have to plan on replacing all the bolts and attempting to come up with a f/ew ideas for (non-welded) brackets to resecure the cable. Any suggestions before I delve back in tomorrow (8/13/22)? Do I need to plan on taking my resonator down, and the heat shield for this replacement?

Thank you so much if you've got anything to offer! (even comments in jest). I'm trying to work this TANK back into inspection sticker worthy territory.

Pics included below of the first one I broke off, and more (f**ks were given during this process, I assure you. I didn't just go ham with a 3/4 drive):

 

Hi Timbukt2 and ChapmanF,
Thanks for the reply. Looks like you and I have similar ideas with getting cars from south of the salt line. This one though I don't have that option to swap out right now (life has its moments), and I'm going to have to get it ready for a sticker. The rust will be fun to deal with, but I'm used to it on cars up here.

Would you or ChapmanF be willing to look over my plan below?

Replacing the e brake cable: #1 - spray all the cable brackets and bolting locations under the rear of the vehicle with penetrant, #2 - spray the resonator (exhaust) flange bolts, heat shield nuts, etc with penetrant, let sit overnight (and make a pact with the autorepair faeries), #3 - support the resonator with wooden blocks, and start removing bolts to get above the resonator and heat shield so I can access the "connection point", #4 either drill and tap some some new bolt holes (large washers on both sides, and probably locknuts), or find a different kind of mounting bracket (any ideas?). #5 replace the cable itself.



Would something like this work?:

 

One more potential option instead of drill and tapping new threaded holes for mounting:

Rivnuts?

 

Aye sir. It would probably flow better with "fellow mogwai". Got to love an 80's classic!

 

Not this one. The tool uses the threads of each rivnut to secure the piece of hardware in the tool with the arms open. Then as you close the arms it wrinkles / flanges the rivnut around the sheet metal / square stock that you've cut a hole in, almost exactly like a rivet. This an the ridges of the rivnut hold it in place.

Speaking of rivets, I might just switch over to using rivets. I doubt I'll need to actually use bolts for removal / replacement later, making rivnuts unnecessary, as this set of parking brake cables or e brake cables will likely last the rest of the life of this 2nd gen.

 

One update from last night:
Using a multi tool and sawzall to cut off and sand down the existing mounting brackets today after the remaining bolts snapped or crumbled. I'm going to make some new brackets out of sheet metal (old screen door, coffee can, olive oil / paint thinner cans) and rivet them into place with 3/16 long steel blind (pop) rivets. I'm going to paint the sheet metal, and secure it with two rivets so that it won't rotate, and probably coat the whole thing in another layer of spray paint or fluid film. They've only got to last another year or two.

A note about trying to loosen these bolts with heat (a mini torch), instead of penetrating oil: it seems like the heat makes a difference with rusted bolts. Careful if you use both though since the penetrating oil is flammable.

BACKSIDE hotwork also needs to be taken into account. Some of these fasteners are attached to brackets that have interior cloth / insulation on the other side of the floor pan. Heating these up (like the ones inside the center "well" where the resonator is) would be a fire hazard on the back side.

Any thoughts anyone?

 

Neat info. I'd only head of people using beet processing waste to ward off ice. However, it would only work down to a certain temp, which wouldn't be low enough for a month or two up here.

Progress:
I've drilled out the broken bolt on the wheel/hub frame, right passenger rear side. (Or is this a control arm? What's the right term here?). I didn't have any metric bolts, so I swapped it out with a 1/4-20 1" galv steel bolt, nut and spring lock washer. (Pics below).

I also found some U channel to cut up for brackets.

Rear drums have been overhauled including the wheel cylinder.

Remaining:
E brake cable reinstall (cut and drill brackets)
Rear right brake line repair (Does anyone know if I can replace a section of steel line with a section of copper/nickel?)
Replace the muffler and bleed the brakes (I know... I know...)