SOHC V6 Conversion Vs EFI 302 Conversion???

[V8LTD]

Hi Im a new member of this forum. I have a 92 Ranger STX super cab that has a dieing 4.0. My father and I want to put either a SOHC V6 or a mustang/T-bird EFI 5.0. The truck will be used for truck kind of work around the house, fuel mileage is important. The 4.0 in it now has 145K and has never been the same since the head gasket went. And I never liked the truck on the hight way because it had no power there just noise. Currently it gets about 16mpg. Obviouly the V6 would be better on gas but is it worth the extra money? My questions are:

If I put a EFI 5.0 in it ( 150, 185, or 225 hp ) what kind of gas mileage should i expect?

which ones easier to do put the SOHC V6 in or the EFI 5.0?

Whats the best conversion book to buy?

I wanted to keep it 4x4 and I have a AOD to put in it. Will the book tell me everything i need to know.

finally there are like 3 or 4 different motor mount types i heard, which one is better the one that requires no moding or the one that lowers the engine in the truck?

any other infor that i may need that i didnt ask is welcome too. I want to know what im up againist.

Either way I go V6 or V8 i want fuel injection.
Thanks