I have seen few different answers to these questions,so thought i would get the latest opinion.
I have completed the rough build of my book chassis / suspension locost and am presently stripping, cleaning painting all the bits for the final build.
It has a 2.0 pinto and box from a seirra on sorn, rear axle from sorn mk2 escort, front hubs from cortina, sierra column, escort rack, Home made wiring out of sierra loom. What will be best way to fill out form to get an age related plate and do i need to do this before contacting local dvla if i need them to give me a chassis number.

I believe you need to have used 3 major components ie steering gearbox and engine. Why not use the sierra steering rack I have used this on mine just needs cutting down to suit I also have cortina uprights. MK can supply cut down racks you would need to specify bu how much you require the reduction

It's 2 major components; see here under 'kit conversions':
http://www.direct.gov.uk/en/Motoring/BuyingAndSellingAVehicle/RegisteringAVehicle/DG_10014246

For 'specialist kit manufacturer' read 'you' as long as you have receipts for the steel.

[Edited on 15/7/07 by matt_claydon]

Thanks gents, what about the process of filling in the forms, getting a visit at home from DVLA, getting a chassis number, in what order does this all happen ?

Richard
You need to contact your local DVLA office as they all seem to have different procedures.
There doesn't appear to be any legal reason why you can't make up your own chassis number (17 digits ) .
Some DVLA want you to bring the car to them (Maidstone does) but others want to do home visits. Some will do this before SVA and some after. That's why you need to speak to your local office and even then they may not get it right!