I could be very wrong, but I don't think there will be a bump steer problem if the R&P is mounted on the axel because it will move up and down on the same arc as the tires/axel do.

Bump steer usually occurs when the steering components don't move on the same arc as the tires/axel.

'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi