Hi Mike,
TRTEL is right, unfortunately. I think the rule is if you can catch your fingernail on a scratch, it won't be possible to polish it out.
I have some pitting in my windshield too (got caught in a sandstorm two weeks after the restoration was finished, dammit!). I think they are deeper than most "wiper marks".
A while ago I was given a windshield that has a lot of "wiper marks", but seems pretty good otherwise. I might try rubbing it out.
Yours is a TR4, right? There was someone selling TR windshields on eBay recently. About $200 if I recall correctly, which didn't seem too bad for brand new glass. The only thing I didn't like was that they were tinted at the top, which the originals were not.
I think the TR4-TR6 windshield was used in a number of British cars. You might find something cheaper, or even locate a good one in a junkyard.
Alan Myers
San Jose, Calif.
'62 TR4 CT17602L