Repairing 305 vs. new Goodwrench 350

[85C1500]

I have an 85 GMC C1500 2 wheel drive with the original 305 engine and TH350trans. The heads on the 305 are cracked so I am either going to replace the heads or replace the entire engine.

I can get a new Goodwrench engine for approx $1700. Will all the parts from my 305, i.e. flywheel, intake mfold, exhaust mfold, starter, crankshaft damper, etc bolt right on to the new 350? I am trying to figure out how much the engine upgrade will really cost.

The other option I have is to replace the 305 heads with rebuilt heads for about $400. The heads are off now and the cylinder bores, camshaft, lifters look OK, however the engine has 100,000 miles on it so I am trying to decide if it makes more sense to just replace the engine w/ the new 350.

Any advice would be much appreciated.