Help picking right offset

[Kmart78]

I am in the process of rebuilding my 72 Nova and am having the front wheels built but I need to know what offset to go with. I plan on running a SpeedTech Pro-Touring complete front subframe and I want to go with 19 x 9" wheels. I got a good deal on tires and already had the rear wheels (19x11) made by Rushforth. I know I am kinda putting the cart before the horse and most are going to tell me to buy the subframe first and then measure for the wheels but I want to get the front wheels made before the style or color is no longer available and it is going to be towards the end of the year before I can get the subframe. SpeedTech already told me 19x9 on a 255 30 19 will fit depending on the offset, but they would not recommend an offset (Liability reasons I suppose). So, is there anyone with a Speedtech subframe that can recommend an offset that will work for my application? Any advice would be greatly appreciated!

[Steve in Pa]

Subscribing because I'll need to do this as well.