On one of my earlier projects back in the sixties I built a glass 27 "T" pickup. I used a Transverse rear spring with just the main leaf and I think the next one or the third one above it. I then mounted coil overs and used Overload type springs on the coilovers. These were the kind all the old time auto supplys sold that clamped over the stock shock. I think you still can get them, try JC Whitney. They were available in three different spring rates, I used the middle rate and the car rode very good, not so bouncy and skiddish as a lot of other buckets. (nobody ever guessed they weren't originally coil over springs).