Call me crazy, but i think a little while ago i saw summit selling there lt4 heads alone for around 630-700 (maybe always like that??), and then the intake is 200 or so. Thats 800 and then you can get your own custom cam for a little more power 230 or so, if you get those lt4 heads ported out make a lot of power, could be cheaper, might be the same cost as the full lt4 conversion, gotta get gaskets and such 100 for the thunderracing cam swap kit, not sure bout the head gasket set, dunno im drunk but check this out,
http://store.summitracing.com/
maybe get a used lt4 intake?? Good luck with whatever you do, should make some power, research is a good thing.
Maybe the lt1 trickflow heads also, someone with more experience/knowledge will know for sure.