If they are the black shocks, and anything like the ones made for spitfires etc, they are not very good. The ancient ones that come off cars are often more effective. If you do not want to spend on adjustables, then keep a look out for NOS ones on ebay etc, but make sure they have the spring pans, often missing and no, they rarely fit from your old shocks.
Re springs, I had some new rear toledo ones from Wins, which gave the same ride height as the originals, which I though had sagged. Bought some used 1500 springs off somebody on here, and they are better, but yours may have sagged? difficult to tell. MAybe measure wheelarch height off ground, and ask for other peoples measurement to see
If I were buying springs, I would be tempted by the 175lb, one inch lower type all round.... but may be too high at the front
Never as simple as it should be.