Getting the heads done on mt gt in a few weeks and was going to go manles ss valves, bps rockers and push rods (so i dont have to mill the valve giudes and can go back to stock if i want) and evt valve springs but recently found out the springs wont work out in this application becase bps parts will be stock lengths and evt's wont.
Basically my question is how much better is dual springs cpmpared to shimmed stock springs, do you really need them ?

their are a few factor to concider find out your installed seat pressure first. Once you know that number see if a single spring with shim can reach that number with out coilbinding. If so the single spring will work but two springs will hold up longer.

Shimmed stock springs worked fine.....until engine rpms were over like 4900 in the water. The dual springs came with some nicer spring retainer end thingies. Didn't realize they were any different in length from the stock springs.

yea, no cam for me, ill just shimmem up. Thanks