Blown head gasket, should I swap engines or... ?

OK, I just checked into the cheap hotel right across the street from Gasket Masters in Manteca. I'm glad my wife isn't with me to note how old and mediocre this place is, but it'll be fine for a night. I'll roll the car across the street for them to work their incredibly fast (and hopefully good) magic first thing in the morning.

The car had been sitting in the garage for almost two weeks before I drove it today, and I listened carefully as it started - very smooth, no misfire! But it did rattle/knock several times at stoplights and some stop-and-go traffic in the first 15 minutes before I got going on the freeway. The coolant reservoir was an inch below the L mark this morning; I'd noticed it dropping slowly since I'd done some work in June, but not that low. I filled it up to almost running out the overflow before I left, and just checked again - it dropped more than an inch during the drive here. Otherwise it performed exactly as usual, reminding me how much I like this car. It's nice to have it here with no further damage - driving 350 miles on a blown head gasket today felt like rolling the dice a bit.

I'll make a new thread when I get home with my report on the work, since this chapter where I figure out what to do is ending tonight. Thanks everyone for your input, I would literally not be here in Manteca without you!