Here's a link to what I did on the Club Triumph Site:
http://www.club.triumph.org.uk/cgi-bin/forum10/Blah.pl?m-1398031871/s-42/highlight-Koni/#num42
The Koni shocks I used are actually for the front of a classic Mini, part number 80-1717, do a search on the Internet, I got mine from a supplier in Leeds, Larkspeed I think, you have to do some modifications though.
1. Drill out the bottom shock bush to 1/2" diameter to suit the existing lower mounting stud/bolt.
2. Change the top shock bush to 2 x superflex SF0365P Top hat Bushes per side, you have to trim a bit off the length on each bush slightly and I Used a M22 (I think) Lock washer each side to get them the correct width to suit the Telescopic Brackets when using the original type Shouldered Bolt.
3. These Koni Shocks are adjustable, coming set on the softest setting, I set mine mid way and the car rode and handled well.
Send me an E-mail to g.flinn318@yahoo.co.uk if the above is not clear and I will E-Mail some photo's
P.S. I had to cut away the Lip slightly to get the Telescopic bracket to fit, if you've not fitted the Body yet then you won't have to do this if you fit the brackets before fitting the rear tub.
Cheers
Gary