Aye Joolz,
I have looked on the WeMoto site and will provide the links further down this message.
1987 XBR 500 H Cam (timing) chain 118 links. Rivet link (NOT RECOMMENDED FOR HOME MECHANICS BY D.I.D. !) Part Number: SCOA412-ASDH-PL
1982, 1983-84 XL 500 RC Cam (timing) chain 120 links. Rivet link (NOT RECOMMENDED FOR HOME MECHANICS BY D.I.D. !) Part Number: SCOA412-ASDH-PL
Both chains supplied by WeMoto appear to be manufactured by D.I.D. and the rivet link has a common part number. Therefore, my assumption would be that the 2 chains have the same pitch and guide system, using the two external plates of the chain.
I had a look at the cam chain for the Honda XR 600 RF/RG/RH 85-87 and this would appear to be the same as the 'standard' XBR one of 118 links.
I have even been sufficiently "Anorakish"

to check the Cam (timing) chain for an SRX 600 as my preferred frustrating motor and this uses the same rivet link as the Honda's above, but a chain of 126 links and uses the two outer plates as the guides for keeping the chain on the sprockets.
Links to Wemoto as promised earlier:
1987 XBR 500 H Cam (timing) chain:
1987_XBR_500_H_ cam_chain1982, 1983-84 XL 500 RC Cam (timing) chain:
1982_1983-84_XL_500_H_cam_chainBy all means clarify with you proposed supplier, as I may have got this wrong! CAVEAT EMPTOR! and all that.

This is the link to the 2007 D.I.D. chain catalogue and the cam chain dimensions are listed on PAGE 105:
D.I.D._chain_catalogue_2007I hope this helps.
My regards, Bill