That's alot of money in shims! Not looking forward to that! ^
I've been worrying about this also. I have valvetrain taken apart and I was personally considering getting the Crower spring/retainer kit to use with the stock cams for now. This would give me a fresh set of springs and the ability to toss in some new cams later when I have a bit more money and can find a good deal on a cam set.
I'm all for the reusing of parts, but the valvesprings in a 1J are about 20 years old... seems like they would be pretty tired and might not be quite up to over-revving a larger cam, or maybe even the stock ones. You would think common sense would say something that has been flexing 20 times a second for 20 years must have some decent level of fatigue, no matter what material it's made out of.
I don't know, it's been worrying me as I get closer to putting everything back together. I'm going to check them for any "lean" tonight, which I've read can be a decent indicator of the fatigue of a spring.
I still haven't decided what I'm going to do, maybe this thread will make me feel good enough about it to re-use the stock setup.