58 power brake question..

[Killrdanasurfer]

Hey guys I'm looking at purchasing a 58 gmc fleet option and the brakes need to be redone. It has a 270 and a floor shift 4 speed in it. Looking around at kits they pretty much all say the frame mount power booster will only work with automatic transmissions? I was wondering why this was the case? I know I could do the firewall mount but I don't like the look of it. So out of curiosity why will the frame mounts not work? Would it have to do with the linkage for a tree shift? In which case I should be ok with the floor shift? Also I found a power booster MC frame mount on eBay that says it will work for manual transmissions.. Anybody have any luck with these? I will be upgrading to disc brakes in the front on a side note..

Thanks!!!
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