Chasing Threads difficult to do; Crank Chainwheel, Visc. '78

Somehow about 5 years ago, I was switching cranks around with the Aerospace crank (the one with big holes) and I think somehow I got the threads on the original Viscount Aerospace crank messed up though it was not damaged badly meaning the bicycle itself was not damaged, the threads on the crank got a bit out of shape but may be reparable.  At some point, I'd like to put the original crank back on. For the past 5 years without any problems, I have had a Sakae crank from that era on the Viscount bike.

My questions:

1.) Is the original Viscount crank strong?

2.) Is chasing threads difficult? It looks like from the LBS, if one has the right tools, it is fairly easy. (my emboldening this because this is really the prime purpose of the thread.

Sakae Crank is probably something like this:

I guess I would generally want to put the original equipment back on but as a practical purpose, the Sakae Crank seems to do well and has for years. This is not a major problem or urgent either at this point.

Thank you very much in advance to fellow Viscount riders.

I'm a bit confounded at remembering exactly what went wrong but since the substitute crank went on and has never caused trouble, I've kind of left the old original crank alone. This is all a bit hazy to me now.

Edit On: Somehow, the thread problem could have been with the pedals; I don't mean to throw a curve or write this post haphazardly, this has now been a few years. I am rather sure, we found out the Viceroy (yeah right), the Viscount pedals would not fit on other crank arms. Maybe this is what I am on about; but I did look at the crank the other day and the pedals are in there secure.

My apologies if this post is confusing, it is merely kicking a few ideas around.