Hi M8
I assume @ least the main bed is ground :) I would apply Engineers blue to a section of the tapered portion of the bed and mark and scrape the tailstock base until both flanks have consistent contact with your bed way, when blueing up make sure to apply pressure vertically directly above the "V".When your happy with that, take a small clamp and secure the base (directly above the "V") to the bed. now you have a reference you can check gap on the flat side with feelers and adjust with file and scraper to get a parallel gap and then make a shim to adhere to the base.
Regards
Mike