I've got an 86 Silverado with a 350, 157,000 miles on it. The timing chain isn't as tight as it was when new, and I'd like to replace it before I have any problems with it. I'd like to replace it with an aftermarket 4 gear setup. Are there any problems with them?

None that i know of or have heard of. One thing for sure though is that you will get a fair bit of noise out of the gears. I do not know what brand you will be going with , but i heard a camaro once that sounded like it had a supercharger in it , but all it was was a set of peter jackson timing gears. Sounded cool anyhow.