HH56 wrote:
From limited research on other cars, I think BTV's all used around the same long stroke, low ratio. The major difference seems to be how and where the pedal was suspended and motion transmitted.

There is a photo somewhere in one of the old BTV threads here of a Chevy mounted high and a Cadillac with BTV mounted by the radiator with a long rod connecting to the pedal. Here is another photo showing a Lincon up at the top of firewall. There is a you tube video on the Lincoln and interestingly, the commentator makes the same reference to sudden failures in the compensator valve and how he advises people to change them out. Threw in a photo of the modern BTV replacement that bolts in for the high mounts.

A Chevy forum says their ratio was around a reverse 1:3. Here is an illustration showing how they did it. Although I can't quite picture what they do to fit a modern unit, because the Chevy is mounted high, is must be a simple matter to get rid of or modify the old BTV linkage to increase the ratio and lower the stroke distance for a modern booster. I think there is a new plate involved so maybe the booster lowers a bit to change the ratio on the long or BTV operating part of the bellcrank.

All the modern units need a higher ratio and the companies say we can't mount the BTV replacements where we do because of that. Since we are mounted as far down as it can go and have the steering column preventing us from going up, we do the pedal change.