Catalyst Conundrum

[J&A]

Title says it all really; I've got a Rev.3 N/A badly in need of a new cat and, as I've just bought a replacement back box I'm pretty skint & trying to save £s where I can!

To this end I've been trawling around looking for a cat and now I'm more confused than ever. My car was first registered 05/94 and has a cat with 2-bolt fittings, elliptical in shape and about 430mm in length (corrosion makes it difficult to judge exactly). Most pages you look at quote a cat that looks very similar but is made to fit 2s made betwixt 12/91 and 01/94, making it apear that it is incompatible. However other sites show an identical-appearing unit, 420mm in length and fitting up to 1996.

The only picture I can find of a post-94 cat shows a cylindrical body with 3-bolt flanges which are obviously incorrect for my car (MR-S?), so can anyone cut a swathe through this fog of confusion surrounding my understanding? Could the dimensional difference just be due to one person rounding up, another rounding down or are there ANY differences between a 01/92 cat and one of 01/94 model?

Please help because time really is limited in this case- I have to sort it ASAP and can't afford to have it off the road for too long. Thanks