the most painless way to do it unless it's the same year/application as your engine, is to pull the intake/exhaust manifold off your engine and bolt them to the new one with all the stuff that's attached. the long blocks(everything from the head to the oilpan) are exactly the same, it's just the sensors and plugs that changed over the years.

'79 sport 4x4 longbed <img src="/forums/images/graemlins/smile.gif" alt="" />
20/22R hybrid with EB's OS valves, 268c cam, offy intake, weber 32/36, thorley header, 5 speed swap, 34" LTBs, downey 3" springs, marlin hysteer, 4.88s and locked

'91 4x4 shortbed
22R-E, W56, the dd!