I did this on a stock '48 Chev. The lower A-arms have a pan that holds the spring in place. Drill out the rivots and bolt 1" spacers. This only drops the front 1/2" to 1", so cut the coils also for more drop. Hope this helps.
47Ratman, try these links: 1937 - 1957 Buick Olds Pont suspension upgrade , H.A.M.B. - Buick Olds Pontiac Suspension Question