Solid body mounts are generally considered to be a little too over the top for street use. That being said, depending upon the mileage of your car and the condition of the existing body mounts, as a minimum I would replace the missing factory body bushings if they have never been replaced and install the GNX body bushings, or replace all of the body bushings and install the missing body bushings & the GNX bushings. I would do the rear seat brace next, regardless of extra holes or not. Front sway bar is of a satisfactory size for most street & moderate handling applications. Several companies make or sell a 1" rear sway bar, or you can go to the 1 3/8" replica ATR rear sway bar, or the HRParts&Stuff rear sway bar depending on the depth of your pockets. Nobody that I am aware of makes a rear sway bar in either 1 1/8", 1 3/16", or 1 1/4", so an increase is either 1" which is not bad but not as effective as a 1 3/8" for general suspension applications, & the 1 3/8" is not as effective as the HRParts&Stuff bar, which eliminates the need for upper control bars, I believe. Mike & Marianne at Full Throttle Speed & Style (FTS&S) sell the 1 3/8replica ATR bar, probably as well as some other forum vendors. HTH
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Fwiw, Kirban's carries the rear seat braces & the stock factory replacement body bushings in sets in about any combination that you want to replace, FTS&S carry the 1 3/8" rear sway bar, & Paul Ferry at HRParts&Stuff carries the other rear sway bar mentioned.
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Drop back by and let us know how you like the suspension improvements as you do them.