Turns out the new exh. valves I got with the heads were Enginetech V1721:
Stem Diameter 0.3715
Head Diameter 1.602
Keeper Grooves 4
Notes Chrome Stem
Stem Diameter 3/8
Valve Length 5.000
This is a little annoying. I'd rather go with 10* keepers and retainers and as far as I can tell, they don't come in a 4-groove variant.
Also, I only got 15 retainers and zero keepers with the heads ...
I do have a lead on a set of Comp Cams springs 995-16 for a decent price here in Sweden.