FRANK S. - I have the new plastic tank on the K321 in my CC 72. It fits the tank bracket fine but the fuel valve on the bottom "plugs" in thru a grommet, no 1/8" NPT threads like the sediment bulb/fuel shutoff requires and NO WAY to tap the proper threads. So you'll need to swap to rubber fuel line, also use an in-lne filter, and get a 1/8" NPT to 1/4" fuel line hose barb BRASS right-angle fitting from the plumbing supply dept. of your favorite hardware store to attach to your carb gas inlet. The shutoff on the new plastic tank already has a plastic 1/4" hose barb molded to it. I hope you have better luck than I did keeping the the supplied gas cap low enough to let the hood close properly. The supplied gas cap is HUGE, very tall.
I'm also curious what Wayne has against in-line filters. I've run in-lines on ALL my CC's & FARMALL Super H for years. I'd have one on the M but it's still got the factory steel gas line and I won't cut it up.
The one in-line filter I retired 5 yrs ago on the 72 would even filter water out of the gas, was an old filter I used on my OSSA motorcycle 20 yrs ago, Pyrex clear see-thru sleeve, chrome plated diecast end fittings, Viton o-ring seals, and the reusable molded nylon filter sleeve had VERY tiny slits to filter the gas. About 15 yrs ago I'd been mowing for maybe 40-45 minutes, the K241 in the 72 started sputtering, running rough, then died. I checked the gas tank, still over half full, checked the fuel filter, some crude in it but the gas looked very clear! I pinched the rubber fuel line off with a pair of Vice-grips, took the filter apart and it was full of water outside the whole filter sleeve, the inside was empty. I rinsed the sleeve off, reassembled the filter, released the vice-grips, walked back to the shop to return the vice-grips and the 72 started right back up when I returned.
The main fuel valve fitting for the float valve in the Kohler's Carter carb is VERY tiny, and the other gas passages are small also, doesn't take much to plug them up. I don't think you can keep your gasoline & fuel system "Too Clean".