It is not necessary to have a front bar in place in order to do a front end alignment.
Without knowing anything more, I think you'll want slightly more than the preferred OE caster spec in order to provide a little more directional stability at the big end. Zero or slightly positive camber and a very small amount of toe-in (less than 1/32" but not zero). Static negative camber settings are for corner-carving; you want the tires at zero camber for straightline stuff (and as the nose rises I think camber drifts toward negative).
Somewhat fussier would be to get the camber and toe settings made with the nose slightly 'up' as it would be during a run, say from 50 mph and faster. Camber & toe while you're in 1st doesn't matter much since the wheels aren't carrying much load anyway, so alignment at low speeds and during large amounts of nose rise aren't as important. The intent here is to minimize tire scrubbing with the car in its actual operating condition, as all of the alignment parameters change as the suspension rises and falls.
A really good shop that understands race cars and their specialized alignments ought to be able to do this for you. So might a shop where the alignment tech is a personal friend and understands what you're trying to do. Otherwise, it's going to be a crap-shoot how well it gets done.
You can always learn how to do alignment yourself, and no, I'm not joking. It's not as hard to do as the fancy equipment makes it look.
Norm