I am wondering if a 1977 351 Windsor block will work in a 1996 Ford Econoline 350 that also has a 351 Windsor. Will the external engine parts be compatible with the 1977 block?

David

 

It might be do-able, but your talking about a 20 year spread on engines, and having EFI now, back to a Carb'ed engine.

In my research, in the 90's era, '88-'93 were the next generation, and '94-'96 were the same, with the roller cam change.
Same being - heads, intake, exhaust manifolds and smog fitment.

Plus, your having to deal with the electronic sensors, along with the EFI working on the carb engine.

If your on a budget replacement, I'd opt out for a used engine replacement, in the '94-'96 range, with the roller cam, that way you have a "drop" in engine, and ready to go.
I just seen in our local Craigslist a guy selling a '95 351W from a Bronco for $400. good price, and a direct drop in engine. you would not even have to change the oil pan (from a 4x4 engine)

I'm working on getting my '92 running from replacing it with a '94 roller cam re-man, but I'm having problems with the fuel delivery, to keep it running.
Had no problems with all the accessories bolting on, and smog tubes bolted right up. Again, the same generation of engine block/heads.

 

The big difference is the roller cam in the 96 motor. You would either have to do a retro fit cam for the flat tappet block or find a similar flat tappet cam to use with the 96's computer. The 96 should be mass-air EFI, so that it can more easily adapt to the different cam. The 96 cam specs out like this: 256/266 advertised duration, .422/.445 lift, 116*LSA