Which bases to get depends on 1) whether you intend to reprofile teh rear bridge and remove the charger hump or not. 2) Type of rings you plan to use. 3) where those existing holes are located if you plan to use them.

Warne and Leupold both make bases that fit an unaltered 98 (one without the charger hump removed. Assuming of course you meant 146 not 46. If you remove the hump, then bases intended for an FN commercail can be used (again, depending on exiting hole location).

I used a set of EAW mounts on this one:

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]