I have not seen a Schneider in years
gross duration depends on what lift If he is using SAE or .004 like a Crane then lets compare with the Edelbrock/ Summit 6400 / Elgin which claim to be 288-298 SAE with intake closing 34 ABDC
214-224@.050 but only .444 lift on the intake
the Schneider says 290 and closing 37 ABDC 224-224@.050 480 valve lift
The Hughes SEH1620 closes 36ABDC has .495 lift but is a much shorter grind at 216@.050
I'd estimate 263@.006 see Howard lobe HM2163318A
The Summit 6401 is also a 224@.050 but only gets 466 lift claims to be 298@.050 it wants 9.5 compression
Closest Comp cam is the XE268H also available from 440 source 224 @.50 480 lift comp claims 268 duration
This could be same league as Schneider- late modern chevy grind
should work fine since you own it- is it new? New lifters? Get the right springs
let's see what Howards and others come up with
The early closed chamber heads take a lot of work to flow so so- I'd get new heads B4 spending money on early heads- unless this is a matching number show car...