I have a 65 Chevy C10 with a 6 banger and a three on the tree. I want to replace it with a small block V8. My main concern is gas milage. I love the V8 sound and feel. I use my truck everyday so I want one that is good on gas. I also want to change to an automatic tran. I have 3 questions. First, would it be best to go with a 350, 327, or 283? Second, what modifications would be best to improve the milage or would it be best to leave it stock? Third, what transmission would be best to use?
Thanks
Shadmo  

The sure ticket to 16-21MPG and kickass performance is get a 4.8 or 5.3 out of a late model truck from the wrecking yard. The transmission will be a 4L60E.
Gear Star for the tranny, and Painless Performance for a wiring harness to adapt the computer to your '65. The lower low-buck route would be a 2=barrel 283 or 327. The 350 is the cheapest one to rebuild... It's all about your budget, and what you want the truck to do when you're done.