Redo heads, or crate engine.

Well, after 290k miles, my trusty well used but excellent condition

First, some background. The truck is a 2 owner deal (I'm the second owner). The original buyer was fanatical on maintenance and upkeep. The truck looks like brand new, everything works fine and other than the high mileage, looks like a 50k miles truck. It's recently had shocks, brakes, tires, exhaust and battery replaced. Last week, it threw a code (cyl misfire #2), and when I pulled the plugs, they were badly in need of replacement (>.90 gap). But up til then, the truck ran fine and delivered 15+mpg. I replaced all the plugs, but 2 days later, the truck got a little warm (270 degrees), lost most of the antifreeze in the rad (overflow tank empty, but rad down about 3/4 gal). Filled it back up with just water, drove it home, seemed fine. Next day, started it up to white smoke everywhere. Now, every time I start it, it's blowing white smoke and sucking water.

OK, so I figure it blew a head gasket, but with 290k miles on the clock, just replacing the head gasket seems kind of silly, as surely something else is going to go wrong (cracked head, sucked valve, etc), or already has.

So I'm debating to fix it and see what happens (about $350 to have someone else do it, or a weekend for me and maybe $125 in parts, assuming the heads ain't bad), OR I have a hankering for one of the new GMPP crate engines, the HT383E. I can get one for just over $4000, but it would give the truck a new lease on life and tow a whole hell of a lot better than it did. Did I mention I do a lot of towing? Boat, bikes, enclosed car hauler.

Anyway, what's the conscientious here? Fix it for cheap and keep my fingers crossed that nothing else goes bad, or bite the bullet and crate engine it? I trust the people here, as they've been very helpful in the past.

Dan