The newer engine will work fine if you swap over the "right" external parts from your original engine. This includes your manual trans flywheel, which has a number of ways it can be mounted wrong and ignition timing will be way off. Check this thread for another engine swapper's story with a happy ending:

http://www.brickboard.com/RWD/index.htm?id=1546641&show_all=1

If you go ahead with the swap, there will never be a better or easier time to check all oil seals in the new engine while it is on your garage floor and to replace the leakers. Check the distributor on the rear of the cyl. head for any sign of oil. And clean or replace the oil separator box, check the water pump for silent, smooth turning and leaks.

So much stuff that is dead easy with the engine out and oh so annoying after you have done all the work to install that engine, and then....
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Bob: son's XC70, dtr's '94-940, my 81GL, 83-DL, 89-745(V8) and 98-S90. Also 77-MGB and some old motorcycles.