Nix the 292 idea. Stock the 292 doesn't have that much more power, and the 250 actually has more power per cubic inch. The 292 is only like 10 more horses. A lot of guys like the 292 and they are a good truck motor. The 292 does have more POTENTIAL horsepower by virtue of the bigger displacement, but it will cost you a bundle to move those horses from the land of potentiality to the land of reality. However, there is no real reason to dump your 250. Especially not if it's an original matching numbers engine. It's certainly bigger and has more power than the 235's and 216's you find in a lot of these guy's trucks. The stock 250 has around 155 horses. If yours really is "original and untouched" it probably doesn't produce much over 100 horses because it is old and WORN OUT.
Here's what I'd suggest:
307 V8 Pistons with new rings of course.
Rod and Main bearings
Cam bearings
A good valve grind done buy a reputable shop
Clevite cam sold by NAPA as The MPG Perfomer. specs are .464" Valve Lift, Intake .490" Valve Lift, Exhaust Duration at .050" 194 Degree Intake 204 Degree Exhaust 110 Degree Lobe Spread. (comes with new lifters.)
Holly / Weber 5200 carb from Langdon's Stovebolt Motor Company. Use Langdon's adapter and stock intake.
Split exhast manifold into dual glass packs.
This will cost about $1000 bucks if you do most of the work yourself. Not cheap, but not breaking the bank either. You get to keep your original matching numbers engine and now it runs around 185 horses compared to the 100 or so you're getting now, and even with those 3.73 gears you should still get 16 mpg on the highway as long as you hold your speed down to around 60 mph. If you want better milage at higher speeds you'll have to go to a more hiway freindly rear end.
Boo
PS
If you decide you want a more hiway freindly rear end, I'll gladly dispose of that old worn out posi for you!
