One final question on this hard starting issue. As I mentioned, I completely cleaned the ground strap connections, which were dirty, and suspect that will clear up the issue. My question is, the original strap is in one piece, not frayed, but does look old. Can age alone increase the resistance on an intact braided wire? If so, anyone know where I can get a new one?

You could check it with a multimeter.

I look a little old, but can totally rock it out.

No, do not replace if it's sound

As long as the contact points are clean, outside patina will not affect function unless you have some severe corrosion or physical damage.

@oakdalecurtis

You can test the ground strap in action to determine if you're losing voltage. Disable the ignition (pull power wire to the coil) so the engine just cranks and cranks w/o starting. Have someone crank the engine while you measure voltage from the engine case to a chassis grounding point. If you get appreciable voltage like over 0.5V, then change the strap.

I replaced mine with a 4-gauge strap from my flaps. They have many lengths available.

And NAPA offers various lengths of braided strap with lug holes.

I mean, if there's any question about it, for $15 why not just do it?

My car never had one as the trans was out and the car a roller.
Made one from a piece of new small diameter welder cable and got a local shop to crimp the eyelets on and all sealed with heat shrink.
Have a second one made up but yet to fit .

I bought a new one, then two.
Fixed it.

I do think that over time they become less effective.
Mine did.

I’m not a pro, but I suspect the large current draw via 50 year old spot welds may no longer meet the original performance.

How much time/money has been spend putzing around with a ground strap? has the starter been checked for proper operation?

yes and yes

a good trans to body ground is extremely important