Hi Rob,
They are pedders jaguar front springs for 350 chev conversion. There are two options, standard height or lowered. Mine are the lowered springs pedders part number 2044. King Springs also do them. Because 350 chev is a lighter motor i believe they are a softer spring than standard jag. The catalogue's actually say jaguar 350 chev conversion so you could just try any shop that sells springs and see if they have a listing.
Some on ebay.
JAGUAR XJ6 W/350 CHEV 1968-86 SEDAN FRONT "LOW" 30mm LOWERED COIL KING SPRINGS | eBay
The cars not finished, but the springs feel ok pushing on it. I wont know till i drive it. Im happy with ride height, currently there is about 90% of final weight on them and they look like they will be about right.