Cab and I both run 4.300 strokes (4.15/2.375 offset ground to 2.200BBC journals) in low decks and my
from 32 yrs of building these things I wouldn't go any longer in a stock low deck block....even if you physically could. More on that later...
In an RB you can generally do a 4.500 since you can get a longer rod in it, depending on your rod length and particularly rod shoulder thickness (e.g., aluminum rods or steelies with through bolts) but you may need to consider a smaller base circle cam as with several SBC and SBF combinations. Long stroke/short rod angles can get so extreme the crank would almost as soon try to push the pin through the thrust side of the bore as it would push the piston to TDC
Back to your low deck...With a 4.5 stroke in a 9.98 deck height with a 6.535 rod you would have about a 1.19"-ish compression height slug on a low deck so it's "mathematically" and physically possible (provided the slug/CW clearance and lower bore/oil pump boss clearancing is taken into account.) The downside is you're going to have a long stroke/short rod combined with a high pin placement. In a stock block with thinnish bores I'd worry more about ring seal/piston stability than I would about 20-ish "potential HP from the few extra cubes.
I will say the 511-518 B combo is PLENTY, trust me on that. I doubt you could feel the extra 4.500 stroke cubes in terms of real world power. There's already more torque than 99% of street cars can harness and up top the long stroke will hit a point of diminishing returns (pumping efficiency/piston speed and ring drag). the 511 it comes on so strong with the 511 package it's really hard to beat in terms of bang for the buck...one of my favorite sayings about everything....just because you 'CAN' doesn't mean you 'SHOULD'...but opinions vary
I even used the stock internal 3/8 pickup that way 
Moving the stroke and the sides of the rods out another .100 may need some more grinding on the pump boss and maybe on the bottom of the cylinders, maybe not 
