direction reverser pops out of gear - Ind 606/2606

I have a problem that the direction reverser pops out of gear going forward. I have to hold it sometimes with my knee. Reverse is not a problem. The linkage seems to pop it into forward and reverse with some play to spare so it isn't a linkage adjustment issue. It does it when I start forward and then throttle up the engine for speed. Any ideas? I hope I don't have to put another bungee cord on it to hold in gear. Thanks.

Although possibly unrelated, I suspect I may have a clutch issue. Sometimes it shifts with no gear grind and sometimes it wants to exhibit some gear grind as iff there is a synchronizer problem assuming these transmissions have synchronizers although gear grinding used to be normal for old transmissions. When I got it, there was no return spring on the clutch pedal. It just put its weight down on the clutch but it does disengage when pressed another inch or so to the floor. thanks.

I guess I'll rig up a bungee cord to hold it in gear till it finally quits or if I need a clutch first. Even Nascar drivers have to use a bungee cord to hold their car in gear sometimes. I don't plan on using it a great amount, (just out at my mother-in-law's farm), just to do misc. farm stuff such as move bales and some dirt work.

The ultimate question is that is it worth spending that much to fix it up? I may check around to see if there might be a gear at a tractor junk yard. Is the tranny, drive train, or rear end about to go also or do those not have much trouble?

I can deal with the regular maintenance, new brakes, fix hydraulic cylinder and valve leaks(although packing kits aren't cheap), probable engine overhaul coming up in a few years(it has plenty of blowby), probable tire replacement coming up sometime (one rear tire is cracked and has a cut going all the way around through the outer layer of rubber)(I hope it just doesn't blow out on me but it appears to have been there for a long time)

Outside of the reverser gear, are the rest of the drive trains reliable?

I may want your help on what it takes to do split the engine to do the work.