New project I have some ???s

[M5-]

I guess this will be an introduction as well as a request for some help. I picked up this 65 stepper a few months ago as I've had my eye on it for several years and the guy finally put it up for sale so I bought it. All and all the truck is pretty solid as it has spent its entire life in Montana. My questions are currently related to the engine. I'll tell you what I have and maybe you guys might be able to figure it out.

The original build sheet is in the seat and it lists the engine code as "UH" which from my research means the truck came with a 292. On the build sheet there is a line entry "4L25AD Optional 170 HP engine" as well as one for the 4 speed which it has. I can't find any reference to a 170 HP engine any place. To further complicate the issue the casting number on the block is 38877178 which can be a Buick/Olds/Chev/Pont/GMC 230-250 from 62-78. Clearly the engine is not a 292 and to verify that I checked the block stamping which is F0414TF which should mean its a 250 built on the 14th day of April in Flint. The date code on the block is D 12 5 which should mean the block was cast on the 12th day of April either 1965 or 1975. The last 6 digits of my VIN are 143503 which I would think means the truck was built in late 65 almost 66. GM switched to the 250 in 66 could they have installed a 170 HP 250 back in 65?. If my engine was a 250 from 1975 it should have the integral head/intake manifold. So I thought OK I'll just look up the head casting number but all I can find on the head is 4888F7. Where should I be looking for the head casting number?

Thats probably enough questions at once. If anybody can help me out that would be fantastic. Here are some pics.


Thx
Paul