One of my valve stems on my 84 300d is stripped, I think. It is either the valve stem or the bottom nut that is used when adjusting the valves. When I attempt to tighten the nuts after adjusting the valve the top nut pushes the lower down so it leaves a large gap between the cam lobe and the other thing...

So, is there a way to fix this without taking the head off? Is it more likely that the nut is stripped, the valve stem, or both?

EDIT: I adjusted all other valves with no problems, this one is the only "sour apple." Its the exhaust valve in cylinder 3...

It is more likely that it is just the nut... and if you believe in Prayer... pray for that because if it is the valve itself I don't know of any way except pulling the head to fix it...
Take off both the nuts...( and for the record... the FSM suggests replacing those top nuts periodically to attempt to avoid just this type situation... but no one that I know of has done this....) and get new ones... and see if that fixes it...

Ok, after thinking about it.... see if you can find a matching nut for the lower one which is twice as thick... that might bridge any stripped valve stem threads.....

If there is no other way to fix it but to pull the head, how about this poor-man's way:

1: get the lower nut out of there
2: coat the top nut with red thread locker (max strength)
3: adjust to a good spec (mabye a little loose for later wear)
4: let it sit over night to set the locker
5: plan in the near future for a head/valve job.

This could get by for a few weeks-months to plan and budget for the job.

How do I go about removing those nuts without shooting my valve into the jug?

I believe the generally accepted procedure is to pressurize the cylinder with compressed air to hold the valves closed.

However, I believe that you can set the piston at TDC and it will be close enough to the valves to allow very little downward movement.

For #3, the crankshaft must be set at 72°BTDC. This might be a bit difficult because of the lack of proper marks on the crankshaft damper. But, you probably can get within 3° with a piece of string and some chalk. This will be fine since the piston moves very little near TDC for each crankshaft degree.