Hi Deni, 180lb/in are quoted as 'standard' front springs for the Spitfire 1500, and were selected to work in combination with a rear swing spring and 7/8" front anti-roll bar.
I found them to give the best ride and handling compromise on my Spyder, even though I had a fixed rear spring, albeit with four leaves removed to soften the back end sufficiently given the much reduced weight over my Vitesse donor.
Their part number is usually either TKC1881, TKC1884 or GSV1030, and their 'weight' spec tends to vary with supplier - Rimmers say 167lb/in for the GSV1030 while other sellers say 180lb/in for the same part number. As you say, Rimmers also have their GSV1030UR, which is shorter and rated at 200lb/in, and if you like a firm ride and the roads you're going to drive on are really smooth then you could give them a go. Oh, and if you use standard length springs you'll definitely need to fit height adjustable shocks or the nose will sit far too high.
Anyway, here are some links to the '180lb' springs, and a useful website regarding setting up a small-chassis Triumph for the best handling. Just bear in mind that your car will be much lighter so you'll have to see what works best through trial and error.
https://www.ebay.co.uk/itm/TRIUMPH-S...4AAOSw7NNT2koF
https://rimmerbros.com/Item--i-GSV1030
http://auskellian.com/paul/links_fil...ents.htm#front
Best of luck getting your car set up.