[Bernica]

[quote=slider701;1019815]I think there are more stuff you need to take into consideration than just the thickness of the existing slab. The first thing I would be worried about is whether you have a tension slab foundation and garage floor.

This is a good heads up. You don't want to cut a post-tension cable (PT) if you have them.

If I was going to do this, and wanted to have plenty of peace of mind, I would cut approx 16"-24" squares at the two anchor locations, then dig a caisson (a round hole) approx 14" diameter and 3' deep with a post-hole digger. Then build a rebar "cage" that is 3" smaller than the hole on all sides, including the bottom. Make the cage with #4 (1/2") rebar running vertically resembling the shape of the hole, spaced approx. 3" apart with the top bent at 90 degrees and inserted all the way around the edges of the existing slab into drilled holes, approx 6" deep. Set these inserted "dowels" into the existing slab with epoxy made for this kind of thing (Hilti product). The cage should also have "stirrups" wrapping around it from top to bottom spaced 4"-6" apart. These are just more #3 or #4 rebar bent around the vertical cage. Use tie-wire to hold them in place. Next, find some good long anchor bolts (12" or more) and some threaded couplers with a size and thread pattern matching your MaxJac hold-down bolts. Make a template out of plywood with hole pattern matching the baseplate of the MaxJac and bolt it to the threaded couplers using spare hold-down bolts. Set the bottom of the plywood flush with the existing finished floor level and fill the hole with concrete (3,500psi or higher strength). After setting, when you remove the hold-down bolts from the template, you should have some sturdy and well-anchored inserts that will resist pull-out and tipping.
Overkill? Maybe, but like I said: If I wanted peace of mind.....