[rustedgoat]

You can easily lower the compression by swapping heads. But rest of the engine still has to be good shape.

Being that your going to be running very low boost not sure how important these are
timing controller
capable fuel system
free flowing exhaust

[mgarblik]

Your opening post pretty well spells out your options. To be brief, IMO, there is no really easy way to take a 389 2BBL engine and plop a 8-71 blower on it and have a pump gas ready, reliable engine. On the other hand, fitting a BBC under the hood of a 66 full size Pontiac and having everything bolt up properly with AC and all the Pontiac accessories will be a challenge as well. Everything is just totally different. Don't know if it has any meaning to you or not, but your car with a BBC, will be almost completely ignored and shunned by the Pontiac faithful. Same as putting a Ford V-8 under the hood. One alternative you did not mention, was to possibly buy or trade for a 71 -74 400 Pontiac V-8 or a 71-76 Pontiac 455. That platform would give you low compression iron heads, compatible with the crap fuel we have and everything would bolt up and be OK for low boost application. A 66 389, even a 2bbl, may have some value to the owner of Tempest or full size from that era for a restoration. Something to think about. I just sold a 455 minus intake which would have been perfect for you with forged pistons for $1500.00. So that's about the typical cost here in the midwest. Good luck.