If you're getting new pistons, get something that is close to zero deck so you will get some compression, at least 9.5:1. The old Silv-o-lite's will work great. That will help and then some type of RV cam to top it off. With new oils today make sure you get oils with zink and or add a lot of it. Flat tappet cams need it and you will kill the cam without it.

Clean EVERYTHING! Use a break-in oil, I know you said budget but this is insurance. Break in the cam and dump the oil. Make sure you keep it clean and change the oil often in the beginning.