Thanks for the pointers all.
Well its on now.. i ended up lowering the main hoop by dropping the bolt where it pivots on the tub bracket. This means I would need to slightly trim down the vertical arm which comes down onto the tub corner near the door latches. Left it for now in case it all settles/stretches a bit.
Also used the door latches from a used but also later model top which meant I could use a piece of angled alu on the tub to keep the doors shut, rather than trying to make up a pin type striker plate.. Looks like there is more than one '80+ bestop supertop version..