The 70 Chevelle SS I bought recently has the deluxe seat
belts that were added by the previous owner. It originally had the standard belts. The retractors beside the front buckets are loose and not completely
bolted to the floor, but I can't figure out how to access the bolt heads to
tighten down the bolts. Since these belts don't have any way of tightening
after latching, I assume that they have inertia reels that lock up in a panic stop? Also, the retractors have black buttons sticking out of the top rear of the retractor covers. What do these buttons do? Thanks in advance for your help.

If they were correct 70 style belts, the female coupler is adjustable and tightens the belt. They do not have inertia reels. You can access the bolts by pulling the plastic retractor cover off. It sounds like someone put later model seat belts in the car.

Well, I figured out how to release the catches on the covers
and now the retractors are firmly bolted to the floor. In talking to the previous
owner I found out the belts were original to the car. I consulted my owners
manual on page 32, and lo and behold my automatic adjusting deluxe seat belts are discussed in detail! Once I learned how to work them they are fantastic! I wish I had a set of these in my 69 GTO! These belts were in fact an option on 1970 Chevelles.

DO you have an RPO code for them?

Don't have any idea what the RPO number is.........According
to the owners manual, if you had the deluxe seat belts, they were automatic
adjusting. The belts that go across the chest are like the standard belts
where you have to adjust the strap, but have brushed stainless buckles
like the belts that go across the lap. Also, the belt buckles on the lap belt
are narrower than the buckles on the chest belt, and it is impossible to
hook them up backwards. Also, the seat belt pockets on the side of the
console have one narrow and one wide pocket, so it is impossible to put
the lap belt buckles anywhere except the lap buckle closest to the seat
and the chest buckle towards the front of the car. I work on cars for a living, and have been in the car repair business since 75, and this is the first set
of seat belts like this I have ever seen in an A-body car, so I assume it
is a fairly rare option. Amazingly, the original belts look like new as the car
has only 68,000 original miles on it. The original seat covers, door panels,
headliner, sunvisors and console look like new as well. I had to restore the
dash and dash pad due to cosmetic issues.