When using available casting, it clocks reservoir so column is decreased. A simple solution is to get a standard plumbing Cu
45 degree, 1.5” elbow which slips over reservoir filler neck with a few thousandths to spare. Gently squeeze in lathe Chuck to make tighter. Insert over neck and secure. Get new filler neck and secure it to top of Cu elbow. On top of new filler neck install standpipe with dipstick that reads proper level. Factory standpipe comes on baby Blazers, probably S-10’s also. Unit is not designed to increase volume, just more easily accessed.
Ed in CO