Edit: apparently this purchase already happened. So best of luck. At least you have a friend who is a mechanic which means you are a lot better off than most of us.
RE: fuel gauge - calculate based on a full tank to full tank. the fuel gauges are screwy on these trucks. But don't expect too much on the MPGs. 15,16,17,18,19 are all totally normal MPGs. If you still have engine problems than the low MPGs could be an indicator.
For anyone else in a similar situation:
I would be VERY cautious about this. If the engine has been properly rebuilt then it should have a warranty statement or receipt of work. I am going through a head/gasket issue right now and will be repairing the truck for chunk of $$. In my case the vehicle never got hot and after the fix, I am keeping it as a DD until Sept then as a 2nd car / camping vehicle. I plan to never sell it, period. If I was unsure of this I would just go the cheap route like most people do.
It is pretty common with engine issues like cracked heads or valve issues, to simply go for the CHEAP FIX & then SELL IT, taking the cash for ones next vehicle. This happens all the time!
The worst part is you won't be able to tell. Unless you are shown the work receipt for the rebuild, you won't know what parts were used. Did they go with remanu heads? valve job? did they use OEM gasket kit or go for the cheap chinese EBAY kit? There are a lot of questions. IMO if someone is selling any car that was rebuilt in last 10,000 miles I would assume they expect issues in near future and didn't want to deal with the hassle.
They probably did the 40,000 mile fix vs. the 100,000 mile fix.
:frog: