Scotty Dog
As you have removed the plastic 'vent' to the rear of the side window, you will see that the offending roll bar bolts protrude a little way beyond the captive nuts at the bottom of the bar (hopefully - they did with mine). The threads should be pretty clean but you should also be able to spray some penetrating fluid onto them so you are tackling the bolt from both ends as it were. I agree with previous comments that your efforts with WD40 or similar on fast-rusted bolt heads are likely to be nugatory, but there is a solution. You will need a dremel, ideally with a flexible extension shaft, and a metal burr bit (ideally several), oh, and a fair amount of patience! Having faced this sort of situation before, I would set about grinding away the remaining metal face through which the roll bar bolts are fitted. If you grind around the bolt heads (allow a little clearance so that you don't chew the heads) you need to work through to the roll bar and then grind down the corner between the two remaining faces. What is left of the smaller face will then just fall away. You will probably find that the now visible face of the roll bar has little, if any rust on it and you will then be able to direct your penetrating fluid to the join between bolt and roll bar. With very careful further grinding you should be able to clean back the bolt head (try to shape the metal left between bolt head and roll bar to match the faces of the bolt head) to get a socket on to. I have ground a bolt in similar circumstances back to a slightly smaller hex to take a 12mm socket rather than the 13mm it should take. Tap the bolt before you try to move with a socket, then just try to turn it a fraction clockwise first before trying to loosen it. Once I had cleared all the rust away from mine, the bolts themselves were not actually that tight.
For what it's worth, I have used stainless bolts, washers and spring washers to refit, but with plenty of copaslip. I did have to clean one of the threads (with a tap), which seemed to have got crossed somehow, but the other 3 were fine.
I used Sikaflex (a polyurethane sealant/adhesive as suggested by Martin - Sikaflex is a tad more expensive than some but I just find it better than most - Partco usually stock it) to bond the turret top in place and then back-filled the gaps once secured with the bolts.
For those of you not using stainless replacements, the best protective coating I have come across is Epoxymastic 1-2-1. Nothing else comes close and no solvent will remove it (well none you or I are likely to encounter!). You can paint any metal, corroded or not, and it's brilliant on the fibreglass inner wing areas. Have a look at
www.rust.co.uk, and just for the record, I have nothing to do with the company! I just wish I had discovered this stuff years ago.
Anyway 'Scotty Dog', good luck with your efforts, I'm sure the bolts will come out eventually - just don't forget the goggles!
Paul T