No worries SS!!
Sometimes there is a stamp on the plate like in the pic below, or it could be stamped on one of the edges of the plate. I do not recall ever seeing it on the back side of the plate, but it could be there. Or it might not be anywhere which I have seen in a few cases.
Measurements CL to CL for lug studs for a 8 x 6.5” are:
The plate is an isosceles triangle
Long 6”
Short 4 5/8”
I do not have 8x170mm plate to measure but the measurements will be a bit longer to accommodate the 5mm (.2”) larger diameter pattern.
The 8x6.5 plate has a 9/16-18 stud thread.
I do not remember what lug spec SMB used for their conversions. It may be listed in your SMB Owner’s binder on the build sheet as to what wheel/tire set up was called out.