By VL/UL I assume you mean the 3-piece threaded covers 1930-38 that screw on to the 45 blocks?
Height is OK for 45, too short for KH.
Probably needs clearance grinding on the fins and flange inside.
Threads mean the alignment must be excellent or you'll never get them started. Remember the KH stems are tilted in at the top, so you need 2 different alignments on each cover (in and back), and intakes and exhausts are different. The spacer/washer between the top cover and the guide flange should be wide enough to cover the top of the cover (don't just use the KH spacer) or it will bend with big springs.
If you're careful you might try to bevel the washers (intake at about 1/2 degree, exhaust at about 3-1/2 degrees), and assemble the stuff with very light springs. Now rotate the washer's thin edge toward the cylinder until the cover aligns; mark it. Take apart, and notch the flange edge and washer edge where they should match before final assembly. You can't use an O-ring etc. here unless you make an extra spring seat that seats on guide flange, and the O-ring only seals the upper cover - more work, more leaks.
The 1940-48 (spring loaded) covers require the UL-only (lipped) blocks, and they use compression to seal; the amount of compression can be crudely adjusted.