Back in high school, when my Alpine was new to me, I bought a Dynoplastic (?) fiberglass hardtop from a pilot who used to have a Tiger. I think I paid $75. It didn't have the rear quarter windows. The front and rear clips were basically L brackets with J bolts in them. Years later, when I had money and restored my Alpine, I bought a decent factory steel hardtop and restored it to match perfectly, all new rubber, all new windows and all correct brackets. I finally ditched that silly $75 top.
Then I came to realize how great that Dynoplastic one was. Glass rear window and sooooo light. Easy to put on and off by myself. Easy to hang up on the wall. Quick to put on and off if the need arose.
And now instead I have a supremely heavy hardtop with plastic rear window, that I can still put on and off myself - but with quite a heft to get it up and off. In fact, I think I've done it only once or twice since restoring it. Of course that's mostly because I greatly prefer top down driving and don't drive it in the rain.
I also picked up a prior factory hard top that had a "little rust." Wow, that was a mess. Really hard to get it fixed well.
So, if this new top is able to fit and be generally water tight, unless you want a concours car you never drive, I'd strongly suggest going this route.