I have used the aftermarket linkage on several 55-59 6cyl to V-8 conversions. It is tight on these trucks as well. I have not installed one with the engine in place however. Also, they have to be slightly modified as they come with a mount bracket for a flat firewall. The mounting location is not in a flat area. Typical aftermarket stuff.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine