It's not impossible to fit a 4.75" stroke crankshaft in a factory GM tall deck big block Chevrolet. But, it's not the easiest or least expensive build to do.
The problem with the factory big block Chevrolet blocks is that the main oil passage runs from the back to the front of the block along the oil pan rail. When clearancing the block for the crankshaft, it's very possible that you will grind into the oil passage.
Also, the coolant passages are at risk of being compromised when grinding the block for clearance.
The oil passage can sometimes be repaired by pressing an appropriately sized thin-wall tube into the oil galley. If you strike water, however, the block will either need to be welded by someone experienced with welding cast iron, or it must be brazed, or it must be fixed using something like a 2-part engine epoxy.
A specially clearanced oil pan will also be required to clear that size of a stroke.
Understandably, steel connecting rods are preferred, and really, are the only option -- aluminum connecting rods simply require too much clearancing.
If you plan on going this direction, work closely with your crankshaft, connecting rod and piston manufacturer(s) as there are many dimensions that must be considered. Using a crankshaft with cam-shaped counterweights will help, as will a rod that is forged with as small of a 'big end' as is possible.
Your connecting rod length will be dictated in part by what compression height piston you want to run and the shape of the crankshaft eccentrics your crankshaft manufacturer can supply.
For example, if you want to run a 6.70" connecting rod with the 4.75" stroke, the compression height of the pistons will need to be 1.12" which is very short. With such short compression height pistons, you will need to deal with the piston pin bore intersecting with the oil ring groove.
It's good that you're planning far in advance because as you can see, there's more to it than just grinding on the block
