Actually, the 1-1/8" master cylinder was used extensively on the GM power disc/drum applications due to the overall piston area of the calipers. The drum/drum applications typically used a 1" bore MC.
As for your application, the LS1 calipers have twin-43mm pistons and the rear LT1 calipers have single 45mm pistons. With a standard '72 Skylark vacuum booster, a 1" bore master cylinder should work well for your application assuming you have sufficient vacuum to run the booster. The LS1 MC would be an excellent choice, but if you're not interested in bending a couple of hard lines to match the MC, then there are other options...but they'll probably require some bending as well. The early 2000 S-trucks MC you mentioned is a good 1" option and has SAE ports instead of metric ISO bubble flares.
The S-truck MC's are available in both left and right hand drive versions, with the only difference being the side of the ports. The RH drive application has ports on the driver's side whereas the LH drive application has them on the passenger's side.
Tobin
KORE3
|