Dunno whether you can use the Jag 1/2 shafts in the Kirkham....
Just so you know, there are at least three different length Jaguar halfshafts.
1) XKE - the shortest
2) 3.8S/420 (or 420G, I forget) - middle length
3) The rest: XJ6, XJ12 XJS, all the big sedans - the longest.
The halfshaft length must match up with the wishbone length - not the same measurement, but from the same car, ie., if you use XKE wishbones, you need the XKE halfshafts.
Lotsa folks use tubular axle shafts. See the ERA web site for their manual in the PDF file to see how this is done:
http://erareplicas.com/
Another good source for info is Mike at CWI:
http://www.cwiinc.com/index.html
Hope this helps,
Tom