You did a great job with the under-hood paint!
There are quite a few members here, like Oldiron440 and others, who has installed a big block into an F-body.
I have plans on doing the same thing, soon.
In my garage are two NOS 400 short blocks, two stroker kits, custom pistons (stock bore), 2-pair of Stealth cylinder heads, aluminum water pump housings and Performer 2186 intakes.
One is going into my ’86 Fifth Ave with either a A727 or a modified A518 (4-speed with overdrive). The other into my ’77 Wagon with either a 5-speed or 6-speed manual.
I see you are converting to Power Steering – which is a good idea. A small block with manual steering is difficult for daily driving. A big block with manual steering is NOT FUN.
The manual steering column intermediate shaft is longer and has a different coupler than the power steering intermediate shafts – so you might want to try to locate one.
Power brakes can be an issue with a big block. Some here has either gone to manual brakes, others have used a smaller brake booster.
/6 K-frames seem to dislike big block conversions, and sometimes need modifications because of oil pump interference and/or oil filter interference that might exist.
I plan on moving my engine oil filter to outside of the engine compartment – because these cars were not designed to access the oil filters (no access from underneath). With the P/S pump and battery tray in the way – they are difficult to access from above. Moving battery to trunk might be something to think about, maybe.
I see you already have a big block A727 (great)!
Do you have a complete 383/400 4-bbl 3-piece kickdown linkage setup?
BudW