The gear are grinding

Possible the pilot bearing is seized to the input shaft. My clutch brake on an 8t #12 was shot. I didn't want to pull the trans to get to it so I left it inoperable. I grease the pilot religiously Will it start in gear with someone holding the clutch down? If it is stuck discs or stuck pilot bearing that would break it loose.

A good practice on any old school manual transmission is to disengage the clutch and make sure the machine is at a complete stop before shifting out of gear. This will completely stop the trans from spinning. Once stopped even apply brake if needed to keep unit from rolling. Now go ahead and shift to you desired gear.

Pull the engine and replace pilot bearing on flywheel end of clutch shaft and also clutch brake if needed.

There are modern replacement clutch brake linings that can be opened up and placed around a shaft and then snapped back closed. I don't suppose you could fit something like that through the clutch inspection cover?

Thanks for the help I'm starting at the brake