Well, there are at least two others of us on the forum who have bought Panny's as well as MonoPrice brackets. The brackets - we both bought fixed models - include a package of hardware; the bolts supplied that fasten the vertical rails of the stand to the back of the set are m8 x 40 mm (I think). I suspect that Panasonic would make those holes into the back of the set the same size across most of their plasma models.
We both have the 50" 700 series. I'm just preparing to mount my set and I already knew that the supplied bolts with the MonoPrice mount were going to be too short so I went to Home Depot and picked up the longest I could find: M8 x 70mm (I believe). Now, as I haven't put the rails on the TV yet I can't be sure if these bolts are long enough or too long! (I also bought 600 mm bolts, just in case.)
As my friend, the other person I refer to, had mounted his set first he let me know that I would need the longer bolts in order to allow for the sub-woofer bulge at the bottom of the set. (Not sure if that applies to the 42" 75 series or not.)
At any rate, there are quite a few bins of these bolts at Home Depot stores. There is a metric bolt section in among all the other types of bolts, screws etc.
Another person on this forum - you'll have to a search - decided with his mount to get better spacers so used #608 wheelbearings from inline skates/skateboards. (Personally, I think the supplied spacers seem okay - the load isn't going to be dynamic.)
Panny TH50PZ700, DSR630, Toshiba HD-A35, Marantz HR-7002, Totem Rainmakers; *C; Toronto