I6 Identification?

[67JimmyMO]

I have been working on "restoring" a 65 K10 for use as a farm vehicle here in SW Missouri for about a year.

To date I have rebuilt the front axle (kingpins/bearings/seals), new brakes all around and rebuilt all 3 driveshafts. Also installed a mini-spool in the rear diff as this truck will never see pavement.

When I got the truck the 230 that was in it was locked up tight but I planned on beating it apart and and doing a full rebuild.

That plan changed when I took the head off and discovered the #5 piston was gone and there's a hole in that cylinder big enough to throw a small cat through!

I just recently acquired a 250 6 popper and was hoping the group here could help me identify the year of this motor. I think it may be somewhat newer as it has an OEM HEI unit in it, but I suppose that could have been added.

The code stamped near the HEI is: F0825CCF

I can provide some casting numbers too if needed, thanks.