Greg-H-

If your engine calls for 6" push rods and you shorten them to say 5.95", when your cam pushes up the lifter and the lifter pushes up the push rod, and the push rod presses one half of the see-saw rocker arm, the 5.95" push rod will not open the valve as much as the 6" push rod. Of course with such a small difference you could compensate by adjusting the rockers, but if the difference were 1/2 an inch that would be a different story.

g0 GMC 253- The 235 and 261 rocker arms and rods are the same length but the 261's are beefier. They are interchangable but the 235 doesn't have the strength the 261 does. Of course you don't want to mix and match a few 235 rods with a few 261 rods, but if you use complete sets I think you'd be okay.

'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi