Billy Shope’s site on suspension- http://www.racetec.cc/shope/
Whether or not there will be pinion rise on acceleration depends on a hoard of things, the basic rule of thumb still applies: Under acceleration you want there to be as close to a zero angle as possible. If that means a degree or two difference between the trans and rear end, then so be it. But there's no correct answer w/o testing, anyway.
There is going to be some deflection unless the links, chassis and all the pick up points are 100% rigid. In a street driven 4-link I'd expect there to be more not less deflection (urethane or rubber bushings instead of solid rod ends, for example) and if that's the case, there's more possibility of some angle being needed as opposed to no angle at all.
I don't know how anyone could discern the OP's intentions were to not drag race it by his post, but then I
assumed anyone doing a back-halved Vega w/a front plate and 4-link w/a 9" rear end planned on using
it, not just profiling w/it. It will help if the OP would elaborate on the chassis, power train, the 4-link and how it will be used.