The original 305 tpi was switched out a couple years ago with a later year engine (i do not know which year). I am interested in getting a new cam, which would give me the best bang for the buck, and require as little modding as possible?

 

Well, it would help a lot if you knew what engine you had now. For example if they swapped in a TBI/truck 305 then it most likely has swirl port heads, in which case a cam swap would be a waste of time/$$$ relative to your heads.
If you still have a roller block engine then the ZZ4 cam makes a nice choice for a lot of 305s. They can generally be had for $50 or so in the classifieds here or ebay. Other than that, the 212/218 comp XR and the one a step below that are two good mild choices depending on your ultimate goals.
This topic has really been beaten to death over the years. You could do a search on these boards and find a wealth of info on the topic to help you make the best choice for you.

 

I know it is tpi, and my goal is to get the most power gain for the money.
For the ZZ4 cam what is the expected hp gain?

 

toss the 305, thats your best gain. i have a 305 and can honestly say i would have been happier if i had just built a 350. trust me, unless you can swap the cam yourself don't waste the time. if you don't believe me reaad my sig and i run at best a 13.8.

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91 Z28, 305 TPI, SLP cam & runners, 3.73 gears, Hedman headers, BBK 58mm TB, k&N, tach, speedo, Hurst short shifter, NICE stereo, alarm w/ window module, MSD 6A, HP Alt., Ported WORLD Heads, Ported and Port Matched Intake Manifold. 99 C5 Rims 17"s in front 18"s out back
EAT, SLEEP, BREATH CHEVY

 

I would go with the Comp cam Xenergy. I am also not sure why everybody is so negative about 305's. Any who know's how to build a small block can make a 305 run just as fast a 350. Good example would be my brother's 81' 1/2 ton Lower Rider Chevy, w/ a 305 my dad has it running low 12's with mildy ported stock heads and stock qjet and intake. It sounds like BS and I though he was pulling my leg too, but not when i saw him drive it!! It just goes to show you no matter how much younger people have experience with engine building that EXPERIENCE ALWAYS PROVALES!!!!!