For the most part, the fuel pump push rods are a 'lifetime' service part for almost any SBC or BBC.
I've never seen a pushrod "wear" so bad at the end that it was the cause of noise in the valve train, or fuel pump system, unless there were major oiling or other issues that had already destroyed or were in the process of destroying the complete cam/valve system.
So I don't think you're gonna find it damaged or in need of replacement unless there are other major signs of trouble, so my vote is just leave it in place unless you see signs of damage or scoring on it (when just looking through the galley cover hole with pump removed) I'd go with the existing rod
Under most conditions you do not need to pull the pump adapter plate from the block that retains the rod unless you notice leaking or see damage to the rod that necessitates replacement..
Almost all SBC's (and most BBC's) take the same @5.75" rod size.
There are some differences in design dependent on some other components, but they are mainly to prevent damage to the cam, not to address any noise or other issues at the pump end.
Latest designs even include a 'roller' end to follow, or ride, on the cam pump lobe - I've already seen one of those fail ...
Unless you need a light weight or other specialty rod for a performance application I would suggest sticking with the 'tried-&-true' GM designs.
As far as the fuel pump,
a new pump should be very tight and hard to push the actuator arm
This is due to several things, the new tighter spring, tighter pivot fit, check valve resistance and so on - unless you have major issues getting it to contract during install I would say all is good-to-go.
While there are some good instructions on this site if searched, here is a link to some excellent install information - http://www.crankshaftcoalition.com/w...k_Chevy_engine
Hope this helps.