273 for 318 swap advice

Hey guys, it's advice time for me and my son, Moose. That 273 we did early this year is a slug. He wants more GO. so we're thinking of up sizing to a mid 70's 318 my buddy will give us. The 273 has a new Comp Cams 270 Magnum solid lifter cam, Eddy Performer 318, Hedman headers,in a 74 Duster with a 904 and 8.25 w/ 3.21 gears. The heads are stock, engine is a 10-1 comp with 160 psi cylinder pressure. This thing needs a shift kit, but it's still a dog.
We were thinking of building up the 318 with the steel crank and rods from the 273, keeping the solid cam and valve gear, and putting this in the 318 with the Eddy manifold, Carter 625 AFB and headers from the 273. Whaddaya think? is this a bad idea? What about heads? I need advice since I'm not too engine savvy and I'm broke and Moose has no job! The reasons for the 318 are purely economical. I have a free one and the Schumacher mounts are 273/318 specific. HELP?!! And THANKS!