I'm guessing yours is one-wheel-peel and not a live axle? Then it is similar to, or is a 605ST.
If it's a live axle, Kartco usually had the axle concealed inside a tube with bearings at both ends to support the axle. Pretty nifty and safer than an exposed axle spinning out in the open. That would make it a model 675 as far as I can tell. More info and basic specs: https://www.gokartsupply.com/kartco.htm
Kartco is/was American made and not cheap Chinese junk like they are now. Is it collectible? Only time will tell.
I saw that "muffler". I guess they really wanted it quieter...
Where's those pics OP? If we positively identify (more or less) this ol' heap, it'll help others in the future.
Tires are give or take (as long as they hold air, right?), but that left front wheel/tire looks like the infamous Harbor Freight junk cart wheel.
Aka the 10" Pneumatic Tire With White Hub...
Those wheels were never meant for a powered vehicle but people see it fits a 5/8" axle and the dimensions are right, so they use them. They're dangerous because the "rubber" isn't rubber, it's like a greasy vinyl that easily disintegrates and the hub and bearings are pure trash. Just thin stamped metal and light duty bearings, like for a hand truck or 2 wheel dolly.
There's a video somewhere of a go kart being driven as the Harbor Freight wheel blows up in real-time. The tire pops and shreds then the rim gets smaller and smaller. Lol.