raise the compression (which means new pistons, balance, and lower end rebuild), add a cam, rebuild or buy new heads and how is propane saving you any money? spend less money, get better economy and more power with gas. EFI systems, complete, costs less than $1200 from Howell. Then you simply bolt on and go.... propane is great for BBQs, but it was a band-aid when it came out. If you really must go compressed gas, go natural gas and get a compressor for your home... then you get the big tax rebate... but even so, where's the savings?