new to me engine - what to do with it ?

Im building a d150 also, my trucks stock weight was just under 3600 lbs. Doesnt really seem to bad to me. If its really bothering you, you can pull the heads, measure CCs have them cut down for compression, Get some thin head gaskets. Im not a big fan of the performer intake, Had better luck with the stock cast iron 360 intake manifold, with the divider cut down. Or do magnum head swap, and a new intake?