76-78 CJ T18 going by the casting #'s
There looks to be a tarp in the background, hopefully it was used to covering it up.
Could you explain how swapping a D300 on a Jeep T18 is more expensive then swapping a D300 on a Ford T18? Both T18s being in good condition, how is it not a real alternative? Unless I'm not understanding your post, it's about a $20 adapter difference between the 2.
If you keep the D20 on the Jeep T18 it cost you nothing, adapting a ford T-18 to D20 is about $500
If you have a ford T-18 it will basically cost the same to adapt a D20 or D300. Being the same price I would pick the 300 at 2.62 gear ratio over the 20 at 2.03. Adapting a Jeep T-18 to 300 would cost the same as well. The adapter price for all the above is in the $520-$540 range. Again, both ford and Jeep T-18s in good condition, on hand.
Side note: If someone has a ford t-18 I have a Jeep T-18 mainshaft if needed.