I've built 6 or 7 4.125" crank SB's...

Only real reason to go over 4" stroke is to add CID/Torque, (generally it's going to add around 1.3 TQ for every inch over whatever you'd have with the shorter stroke crank), & to lower the intended powerband. Figure usually around 200-300 RPM difference between a 4" & a 4.125" all other things being same.

For a basic street/strip type deal.... availability of a huge selection of off shelf pistons is why most would stick with 4" stuff.

But if for some reason you are building a combo that you know you're gonna do a custom piston in anyhow... then sometimes we look toward the bigger stroke stuff.

I usually use a 6.20" Callies Comp Star rod on them, although I did do a couple 6" ones before where I turned counterweights down.

Rod bolt clearance to off shelf internal oil pickup tubes can get real tight... other than that... it's just a rotating assembly.