A 7" booster is about half the size of what would be appropriate for a power drum brake system on that vehicle. Looking at the pedal boost available with that size diaphragm, you'll only have about 1/3 the necessary pedal thrust increase. Better than nothing, but not much!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!