Take off about thirty of those:
- Swoop and Bristleback appear twice in the list for some reason.
- Blurr, Hot Rod, Kup, Cyclonus, Scourge, Blaster, Inferno, Prowl, Snarl, Wheeljack, Megatron, Shockwave, Soundwave, Sideswipe, Tracks, Bombshell and Thundercracker each appear twice despite their two incarnations being the same character.
- Likewise, Optimus Prime, Bumblebee, Grimlock, Jazz and Starscream each appear three times when their respective toys represent the same character.
- I haven't counted them amongst the 30, but obviously characters like Goldbug, Rodimus Prime etc. could be argued to be the same as their counterparts. Also, Omega Spreem may or may not be the same character as Omega Supreme. Similarly, characters with the same name, like Motorvator Lightspeed could be Technobot Lightspeed, but I haven't counted them either.
So counting only original 80s-90s G1 toy characters there seem to be about 412 (not including toys retconned into G1.)