I just purchased a DEFI electrical boost gauge to replace my Pettit mechanical. Now the DEFI has a hose connecting the gauge with a t connector on the engine end. There is gets connected to a line running from the top of the Fuel Regulator to the surge tank.

Can't I just swap the gauges, and not have to redo the sensor feed?

Obviously I need to adapt the power/ground/etc also.

(Going into an FD)

 

where ever your Pettit was getting it's vacuum source, un plug it from the back of your gauge and plug that into your defi boost sensor. That's all you'll need to do.