you may want to re-consider the transmission / shifter swap. While changing the internals and eliminating the slick shift is a good idea for street /show car use, I would leave it as your FIL built it and keep what was very common in the late 60's and early70's with the HD 18 spine B/E body tail shaft 833 and shifter relocate.
internally, I did exactly that with the aluminum case 833 The California Flash restoration. The slick shift goodies are still on the self. The standard internals are easily found.....not exactly made out of unobtainium.
The Flash was built in 1975 with the short tail shaft transmission, but numerous A bodies race cars and hot rods used the longer tailshaft / B body trans. IMHO, it's a period correct modification....and friggin cool.
you will have a blast with your ride!!!
View attachment 1716079715
View attachment 1716079720
View attachment 1716079721
View attachment 1716079722
View attachment 1716079723