Cam bolt washer?

Buttoning up the front of my 318 stroker I found that the concave cam bolt washer needs a spacer to bolt down the timing gear as I have no fuel pump eccentric.
The motor was previously run with a flat tappet cam so I guess the whole end play issue was ignored.

What thickness spacer am I shooting for? Or is there a replacement washer specifically for motors without the eccentric?

Thanks