First of all learn to spell second how many cylinders dose it have. We can't tell you anything with outsome knowledge about it.
For '81 you had the 351M that pushed 148hp stock, the block was a 400ci block with 351W heads but the deck height has been shaved down. Carb was a stock Motorcraft 2 barrel. The distributor is the stock Duraspark ignition system (junk) btw. The 351W pushing close to 230hp block was the same as the 351M but with 4 valve heads and a stock motorcraft 4 barrel with the Duraspark ignition system. Then you have the big badass 460 pushing an even 300hp, carb either the 2 or 4 barrel motorcraft and the duraspark ignition system.
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