I'm about to put a Holley 600 VS onto an Edelbrock Performer dual plane manifold when they arrive next week. Done a bit of research and realise I should use one with the four holes. 16mm thickness is OK for me. Do you need the bore size or do you already have one in stock? I wasn't aware of the problems with heat cracking the plastic ones. Anyway I like the sound of yours and will order one next week - how do I pay?what carb is it for and what thickness, i have some in stock, i will look later.
this is what i might have http://www.rodsnsods.co.uk/forum/traders-sale-services/phonolic-carb-spacers-30293 they are cnc manufactyred from top quality phonolic resin plate (not moulded plasic like the cheap ones are) so dont crack or get brittle with age and heat.