You have a great car to run a 250 in, so just patiently work through the learning curve, and you will end up with a really cool hot rod.
I wouldn't recomend fooling with ebay to much. Most stuff sells for way more than it's worth. Scouring your local wrecking yards and swap meets is a better idea. Along the way you'll meet good people and build lasting and valuable freindships.
You shouldn't pay more than $75 for a head because all you want is a rebuildable core. As for a q-jet, you should be able to find a good one for under $50. I know guys that have buckets full. The thing to decide is how wild are you going to go with your build. The q-jet came in several sizes, and you do not need a 650 or 750 cfm carb for a mildly built 250. For example, the engine I described above works good with around 400 cfm. That leaves a bunch of options; a pair of Carter YF carbs, a 425 cfm Rochester 4GC off an old small block, a Holley 390, a Pair of Holley/Webers, et. We could easily add to this list.
Get Santucci's book, plan your work, and then patiently work your plan.
boo
