these are easy, all you need is 1/2" drive breaker bar or good impact gun the bolts come right out, theres only four of them holding down the cab just like on full size series, they are smaller than those though
jc whitney and the likes will have cab mount bushings,
simple
or do you mean the metal cab mounts are gone ?
if so then you should just find another cab, good solid ones can be found in this part of the country, yes alot are ate out, but you rarely see any with cab mounts rusted out, but all the time the cab corners are gone however, but thats easy fix with a mig welder and grinder and a little putty, cut just enough metal off to get to the clean solid, cut off as little good solid metal as possible and cut out same size shape from new patch panel, fit in place and flush and use small body tap hammer if necessary to make it go flush all round, tack in place where you have made it flush, and do same all around the perimiter of the panel and then weld it in place about an inch at a time and stop and let cool, then go another inch and let cool again til all welded up, then grind and tap welds smooth and/or maybe a hair under, and use alittle filler over the welds just like as if you are taping drywall seams, spread it out good and smooth and then let cure and sand nice and smooth and perfect
a little practicew on a junk cab or something would be best, once you get hang of it then you got it forever, and you can make side money often with this skill, its not that hard if you take your time and such
good luck
