I have a 81 F250 with a 351M stock.

(1) Where can i find aftermarket exhaust headers to fit it?

(2) What kind of cruise control set up did the 81s have?

(3) How hard would it be to make it four wheel drive?

that is all i'll ask. I'll ask no more.

I have a 81 F250 with a 351M stock.

(1) Where can i find aftermarket exhaust headers to fit it?

(2) What kind of cruise control set up did the 81s have?

(3) How hard would it be to make it four wheel drive?

that is all i'll ask. I'll ask no more.

(1.) Ant of your basic aftermarket suppliers, i.e. Jegs and Summitt. If you wanna get ripped off, use those. Suprisingly E-bay has a great selection of aftermarket headers for your truck, great priced as well.

(2.) NO Idea.

(3.) I wouldn't try a 4wd conversion unless you are rich and have a donor truck in great condition. You'd be better off buying a setup with 4wd already in it. In other words, i'd be hard.
You'll need:
New tranny, Transfer case, front end, front drive shaft, various front end suspension components, new rear drive shaft, the proper shift linkage, alot of money and time, and a good relationship with the car gods wouldn't hurt.

auto zone has a cruise control kit for a $100 bucks made by audiovox. Is it any good?

Thank you for the info.