I have two Z's with missing driver door springs and have seen a few others with the same problem.

I discovered this $7 tool and hope to use it to insert a new spring with the hinge on the car.

That kind of looks like the tool I use for similar jobs and I think I've even used it on Z door springs or one of my other Datsuns. Mine is a 'small engine valve spring compressor'. I guess it's designed for lawnmower engines, etc. Had it so long I don't even remember where I bought it.

Can you say where you bought it from?

Thanks

Here's one.