Historic Formula Ford 2000 Association

Against my better judgement (hate the place!) thinking of banging an entry in for Thruxton. Having not changed any ratios in the box over the last two years and only running a 21.29 3rd gear and 24.28 4th gear it's obviously going to run out of puff so going to have to buy either just a 4th gear ratio or a 3rd and 4th ratio. Opinions please on choice of ratios and the best place to buy them from. Ditto for Silverstone GP cicuit as well please.

According to 'zee list' for Thruxton its:
10:31CWP - 14:36 19:32 22:29 25:27
9:31 CWP - 15:36 20:30 23:27 26:25

http://www.historicff2000.co.uk/FF2000Ratios.pdf

I used the 25 and seemed about right. Heard others say they have used a shorter top but I think I have too much engine-sympathy for that...

Silverstone HGP gearing is a bit more of a compromise but I recall 24:27 top is about right (with a 10:31) unless someone confirm differently...

Ken would have something I'd have thought. Otherwise I've bought new from: http://www.hewlandclassic.com/

Bit of a problem finding someone with preffered ratios in stock so leaving third as it is and gone for a 24.26 top, thanks for advice.