To benifit from coil overs you need to have corner balancing done and your geo settings, this will cost about 300 quid. Gatwick subaru did mine and Worzels, they take the car to a specialist for the balancing and then they set the geo up.

Guys if buying second hand, make sure the height adjuster rings are free and good condition,make sure the damper ajusters are free and move from soft to hard ok.
I would suggest if your buying from jap performance, check there web site to see what they have and then do a google for some review data.

Jap perfomance have a good few sets of coil overs for classics at the moment, They generally ask for up to 70% of new cost, so make sure they are spot on.

I know worzel got a mint set and they make the car sit and feel awsome.

Good luck