Does anyone have access to a reference book for thermostats?

In case anyone has knowledge, I need a cold-opening 52mm dia unit.

Cheers

I think you can download one from Valeo?

a quick search found
this
https://www.hella.com/hella-za/assets/media_global/HASA_Thermo_Range_Borchure_LRes.pdf

I’ve managed to order a suitable-looking one for modified MX-5s. We’ll see if it fits!