Here are the bore sizes.You may find googling specs of a particular size/bore master cyl. Sometimes using orileys/AutoZone etc look up it will have the specs in the description. Obviously aftermarket wilwood eastwood etc racing brands will list bore stroke and everything else.
With that being said if you are using the clutch out of the same vehicle your transmission came out of you already know you have the proper internal slave.
If you find them on google it will most likely be to a thread where someone has done an nv4500 or 3500 tranny swap in a jeep or Toyota or other vehicle and had similar issues.
I want to say the 4500 and 3500 had the same internal slave or maybe its an assembly with the hose attached. Its been ages since i looked into those transmissions in detail.
My low profile clutch choice was to help me not have to mix and match master/slave cylinders and reduce headache on swaps. You learn more on your first conversion than any other.
I did a quick Google search. Many people use the nv3500 in different swaps to get a cheap mt with od swap. Many have had throw issues
It appears that Some say the slave should ride the fingers at all times. Some say a .060 gap. Spacers can be purchased to make it sit closer. If your isuzu had the same master cyl as a blazer you should be good with your master cyl. The full size and blazer/s10 nv3500 are all integrated bellhousing and should have the exact same depth from one to another. Should is the key word here. The shifters are probably shaped differently.
Isuzu 1992 clutch master: Integral Reservoir Type, 0.630 in. Bore Size
1994 4.3 S10 nv3500: Master Cylinder Bore Diameter (in): 0.88