There is a lot of machine work done to make one of these heads flow/ perform. 500 Holleys go from 50-150 all the time. Bought one this spring at a swapmeet for 20.00. With the stock cam/ head expect to go from around 140-145 hp w/ 220 tq on your worn engine to 200 hp and 275-280 tq. Do a cam and head work, then you will build much more tq.
Take your time and fab up a strong downpipe. While you are at it make a stand that bolts to engine mount to help support the weight of turbo.
Inliner Member 1716 65 Chevelle Wagon and 41 Hudson Pickup Information and parts www.12bolt.com