what is the loppyest cam i can in stall with out changing anything else on my lil 305 got a 2500 stall converter was wanting a cam with the same rpm range and a holley high rise single plane intake

 

What's your primary goal, having a lopy idle, or the best performing system?

A high rise single plane intake is not the right way to go. First, it won't have the proper power band. Second, the q-jet won't bolt to it, meaning a squarebore to spreadbore adapter, which will reduce hood clearance.

What year is your 305? If '87, then a ZZ4 or LT4 Hot Cam would work well. If '86-earlier, something like a Comp XE268 would work well with your 2500 stall converter and a Performer RPM spreadbore intake manifold.

This is assuming you have headers, full 3" exhaust, and something other than the single snorkel air cleaner already.

 

being an s-dime, it probably doesn't have a 3" single exhaust, as noone makes one for those. A good 2.5" single exhaust can support 270 crank horses without restriction, and odds are that 305 won't be there with stock heads. I agree with Five7kid about the cam and the choice of intake manifold. You'll want at least a 3.42:1 axle with a 700R-4, and a 3.73:1 with a 200-4R.