As Joel said, I replaced mine with F-body belts. They do not disconnect at the buckle like the original ones but the retractor under the seat goes away. Thats where most of the issue comes from. They also are longer so my heavy friends have more room to buckle in with.

Does anyone know how to clean seatbelts to appear new?  My belts are in good shape structurally ( no rips, etc) but they have some ground-in dirt that I would like to remove without damaging the belts.  I am aware of the http://www.ssnake-oyl.com website but I was under the impression that they are kind of pricey. Thanks.

Hey chuck believe it or not I keep baby wipes in my car and in my box at work..they clean everything..and get the grease off my hands..I figured this out when I worked on the car at home and had some in the diaper bag..I was out of paper towels..it also works on that black goop that is on the steering wheel..when I got my car the belts would not move at all..I couldn't adjust them at all..I just have the lap belts..I worked at getting them loose then wiped the heck out of the belts and they work good now..if you have the retractor for the shoulder harness run one thru where the belt glides and it will clean that out also..the only thing you don't use them on is real leather..it works so good it went thru the die on my trucks steering wheel..oh well I got the die and redid it..other than that it hasn't damaged anything..and I have cleaned the car with them several times..if they are real bad you could soak just the belt in some soapy water overnight and wash the dirt out that way also..mine were not that dirty as I had some rust inside the buckle..
Rich

Thanks, Rich, for the suggestions.  I think I will try scrubbing them with soap and water.  I am the original owner of my Vette and it has about 31 years of dirt worked into the belts.  I think they will require a little work.

I've got a 74 conv and finding OEM belts for it was not fun at all. I managed to find some on ebay, but they weren't cheap. In the end it cost me $800 for the lap and shoulder harness. The upside? They look friggin great.
I got them from these folks.
http://shop.ebay.com/corvettepartsking/m.html?_nkw=&_armrs=1&_from=&_ipg=25
Good people, just not especially cheap.

I just purchased mine (still waiting for delivery) from Andover Restraints. They had a big selection and reasonable prices

For the UK folks I just fitted Securon lap belts to my 70 convertible, the belts that came with my car had Chevrolet buckles but were dated 1973 so clearly weren't original and as they were way too short probably not even for a Corvette!

Without removing the seat belts..this works pretty well for belts that are not damaged, pilled, frayed..

I ordered a set from SEATBELTSPLUS.COM for $240 for my '75.  I haven't installed them yet but they seem to be good quality.  It looks like the economy style with shoulder belts are $270 now.  The OE style is $340.  I don't remember how many places I looked before I bought but everything else was more expensive and I didn't want to trust my life to some unknown quality recovered set from ebay or something.