Installing an automatic trans in my 4spd truck, where would be the best vacuum port?

[rocketwheels]

I realize I need a vacuum line for the modulator valve (got a turbo 350 going in). Where would be the best place to draw the vacuum from? The truck has a centerbolt head 350 from the 90's , has an Edlebrock alum intake and also 4bbl. Truck has added power brakes. Truck is a 68 K-10.

Could I add an extra stubb where the power brakes draw from? Or should it be somewhere else. I know how the modulator works, but never really thought about how the vacuum works in different places on the engine.

As a side note, planning on using a Lokar or like style of shifter and keeping the simple steering column. I have the different drive shaft and crossmember that matches the trans. '68 = no backup lights so not worried about neutral safety switch.

Anything I'm not thinking of?