There have been several useful recommendations offered that have the potential to do what you need. Given the criteria you mentioned, I'd like to offer my take. If I were in your position, here is what I would do.
I'd just clean up the block, give it a 0.030" over-bore, line hone the mains, tank it, etc. I'd clean up the crap in the ports and bowls, and give it a good 5 angle exhaust and 3 angle intake valve job. For the cam, I'd use
Comp Cams 252 mechanical grind. Stuff like ARP fasteners, magnafluxing and so forth would help.
Next I'd get a Super Six 2-bbl intake manifold and 318 Carter carb. Refer to the
Turbocharging articles I wrote for Allpar.com many years ago. I'd modify the exhaust manifold so the standard Dodge 2.2 Garret Turbo bolts right on. Plumb a 2.5" exhaust the entire path. Limit boost to around 8 psi or so. I started running into issues around 10 psi without more hardware (blow-off valve, intercooler, etc). This will give you excellent cruise MPG with Low-Comp 340 type power when you need it. This would be an excellent package for towing as well.
