The stock factory pushrod is a very good product and does not need routine replacement! The strength and size of the pushrod is ideal for the A-series motor. The narrow body of the rod allows for a very high lift cam without fouling the pushrod holes of the cylinder head. Check they are straight--roll them on a flat surface. And you should insure that the end of the rod that extends into the lifter is still smooth. It should not have a tip on it; this is typically so well worn that it almost looks stock but it actually is worn so badly that it was cut by the hole often found in the seat area of the inside of the lifter. Pushrods should be replaced as a set except if you have bent one on a race motor.
There are two lengths; 2A14 for small bore (850-1100cc), measuring approximately 8-7/16" and AEG314 (1275cc), measuring approximately 8-3/4".