We have put some long engines into AD trucks and it does take some knowledge, quite a bit of engineering/fabricating skill, and lots of patience. A real drawback of the Art Deco and Advanced Design trucks is they are already cramped for inside cab space so a recessed firewall is not the first choice. With an inline engine the factory recess in the firewall could be extended back but this would best be done if an automatic trans was used. The upper air baffle plate containing the hood latch can be notched and the "U" shaped core support replaced with frame side mounts as was done on the pictured Coca Cola truck with an inline 6 turbocharged diesel. On a half ton pickup increased front end weight must be considered. There is a man on this site that has put a Vortec 4200 Atlas engine in an AD which is IIRC close to the 34.5" length of of a 320 Buick straight eight. I have driven a 37 Buick Special with a 263 straight eight for about 40 years and know first hand how smooth they are and the low end torque is outstanding. They are NOT a hot rod engine as even the top horsepower of a 320 is 168 which is the same as a 1955 Chevy 265ci engine with a two barrel carb.
Upper air baffle notched all the way to hood latch plate:
[img]https://i.postimg.cc/dL6kY6kf/IMG-4399.jpg[/img][img]https://i.postimg.cc/xkMNW2Kv/IMG-4403.jpg[/img]Firewall not altered:
[img]https://i.postimg.cc/ppS9rTCQ/IMG-4400.jpg[/img]
