The aftermarket V-8 linkage works OK with the stock pedal. The problem that I have found with them is that the upper bracket is made to mount to a flat surface but the correct location on the firewall is curved. I had a discussion with the Truck Shop about this issue several years ago but they are still selling the same unit. It can be made to work. I think all the aftermarket suppliers sell the same part. It will work with a 4bl as well.
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