well, I'd be inclined to keep the 318 together, and in the interim, get another to build. that way the car is only down for a weekend while you swap motors.

for a motor, I'd look for a 318 magnum, get an edelbrock magnum air gap, get the roller cam reground by bullet cams with their HR259/316 lobe for intake and exhaust. hughes #1110 springs with junkyard 2.2L retainers, a 600 edelbrock carb, just rering/rebearing the motor, maybe do a little touchup on the heads. you'll be very pleased with the performance of a magnum headed 318. it pushes my 3900 lb boat into the 14's...