Derek,
You should go back to the 1973 IMLEC when Pat Killian, IMLEC's first lady driver won the event with her father, Bill Longstaff's L1, built to Clarkson's drawings.
Clarkson's L1 is a very good design although it is slide valve which isn't the choice of many 'true to prototype' modellers these days.
I'm sure there will be someone out there with a set of drawings that they will sell or allow you to copy, but be warned that Harry Clarkson was not into minute detail and left a lot for the builder to work out for himself. When people complained he usually told them that we've built a lot here (in the factory at Layerthorpe) and we haven't had any problems!
A lot of his most popular designs were built ( I did his A4 in 3 1/2" gauge) and it is unfortunate that the patterns and drawings disappeared, because for the most part they were of excellent quality in terms of their fidelity to prototype.
If you are really keen to build the L1 and are prepared to do some drawing work, then I would guess that most of the castings for Don Young's K1 2-6-0 will be of use, and the drawings could be modified for the L1 since it was effectively the tank engine version of the K1 which Clarkson also did drwings for.
The boiler is probably identical and I would guess the bogie is close to that of a B1 or A3, both of which are available from suppliers. I think Reeves have all of Don Young's locos in their catalogue.
I don't know that you will get such an easy start with the 4P, I can't say that it is often modelled.
Which ever loco you decide to build I hope you are successful and find the work fulfilling.
Regards
Eddie
Edited By 61962 on 21/12/2012 22:53:57
Edited By 61962 on 21/12/2012 22:54:37