Re: Carby turbo 250 cross flow....
Any forged pistons are good, just avoid the lightweight racing ones. I have speedpro in mine, but I would just go the cheapest you can find.
4 barrel gives you the ability to tune the motor better, you can jet the secondarys up to supply fuel for boost, and still run a sensible size primary. A 500 2 barrel could be modified to work well, would be alot cheaper than a DP too. Dont use vac secondary carbs, its too difficult to mod them for boost. And dont go a suck thru system.
You will only need a cooler above 10 psi. A cooler will set you back $600+ for something decent.
I have no idea what a reco t4 is worth. they tend to be expensive because everyone wants em.
Whats your budget for a motor, and how much fabrication can you do yourself?