The correct lines for the 3/4 truck are 1/4". Since the original lines are 1/4" and if the new wheel cylinders match the originals, the fittings on the 3/16" lines will be too small.
Have them send you the correct lines.
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