The only Makcs that were reissued in plastic were the R-Series & the Cruisliner from AMT/Stevens International. They've been out of production for a while now, so you won't find any at Michael's or Hobby Lobby. Italeri had a Superliner in plastic, but I don't know when that was reissued. You might be able to find on on eBay.
As far as old Macks; I recommend checking out American Industrial Models. He has lots of old Mack conversion kits as well as complete resin kits of the B-61, LJ, & LT. That's about your only chioce for "old" Macks. Illini has some old Kenworths, Internationals, Diamond-T, & Hendricksons; and Eric @ P&P Vintage Kits & Resin Works has some old Kenworths.