Also consider that the difference between a 230 and 250 is the crank shaft and rods. Then look at the thread in the "Hi Performance" Forum, "Dyno day for a 250". The information that will be available will be real numbers for performance mods. Then if you shop around you will find out how much HP you can afford.
I bought an RV cam from J.C. Whitney for about $110 with the ride. It came with a set of lifters, no cam card.
You can also look for an exhaust manifold with 3 bolts on the flange from a 292. This exhaust manifold has a 2.5 in open vs the 2 that 230/250 manifold has. I bought new long tube headers off ebay for less than $100. Patience,,,,
Larry