I am afraid that this would give an erroneous reading, reason is that 
     the line to the booster is likely protected by an anti-backfire valve 
     (at least it was on my '71) which would affect the readings.
     
     BTW, I learned about this the hard way on the '71.  I left it off in 
     the course of a Type IV conversion and was rewarded with a ruined 
     booster, not because of backfiring, but because of gasoline ingestion.
     
     -Blaine