The Riviera GS had firmer shocks with bigger stabilizing bars and better brakes. Despite its weight the car was quick and agile.It was a strong seller in the luxury personal car market back then and now a loved collectible.
Your electra 225 convertible is a 1968 model, one of my favorite model year from Buick. The car featured a 430ci 360hp engine delivering 475 lbs/ft o torque @ 3200 rpm which was a strong and very reliable engine.
The 350$ dollar Riviera is a 1971/1972 Riviera Boattail, one of the best designed Buicks in the 70's, in its standard version the suspension was too soft but when ordered in its GS version, it was definitely quite a hauler and very great handling car despite weighting near 4500lbs. An expensive car to restore but well worth it.
Regarding the Regal Type T , a close friend of my cousin had a Regal GN-X but knowing his love for horsepower, he removed the original v6 and installed a 455ci crate V8engine with double turbos. He owns the car since 15years and even topped 160mph one day. On the track his best quarter mile time was 10.2 at 129mph.My cousin often goes on the track racing with this guy who is one of his best buddies since they served together during the Bosnian conflict in 1996.
Pleasure is all mine of remembering good old cars memories
HAGWE
Best regards
Georges