two questions
 

1st did i get a good deal i traded a 1996 maxima with blone motor and $1000 for 1972 c10 long bed has a irok 305
2nd what's a good 5 speed trans for it that will give better gas mpg its only gettin about 6 mpg now or other tips to get better

Re: two questions
 

So, you went from a Nissan that did not run to a truck that runs, but gobbles gas like it is going out of style. Gas mileage improvement was zero or negative in this case. The fact that you can drive down the road is a plus. The old Camaro engine must have something seriously wrong with the way it is set up in the truck to get that low of a mileage number. I would check timing and the basic items to make sure there is nothing wrong there. As for a tranny, a six speed would be better, but the install could be a major issue if you do not have the right background or equipment. The IROC engine install, is it a complete install with all of the IROC parts, or is it just the block with the truck's components on it. (carb, etc...) If the engine is trying to run on the computer then there could be issues with how the computer was connected and the sensors are reading the exhaust and coolant temp.

Re: two questions
 

It has a 4 barrel carb don't thank the computer was installed

Re: two questions
 

Some of the early IROC's did have a carb. The TPI was actually an option that most had.
What gears are in the truck? What cam? 5MPG may be normal if the engine is seriously over cammed and crappy gears and so forth.

We need to know more about your truck to give pointer to get better mileage beyond a full tune up.

Re: two questions
 

Original 3 speed to the truck and stock cam as far as i know

Re: two questions
 

Was it a 6 banger truck? Serial # starting with "CS"?
You probably have 4:10's in the rear... helps explain some of the 5 MPG.

Re: two questions
 

Ok every thing i know is its a 72 c10 long bed (350 3 on tree) all is stock but the motor and swifter moved to floor
Motor is an 89 iroc 305 changed over to a edelbrock 4 barrel