If your going to have the shortblock assembled by a shop I would get a price on getting the long block assembled. I'd bet there wouldnt be a big difference and you'd have peace of mind knowing the heads were torqued properly. Also if something unspeakable happens and your engine blows within a month, you may get some help from the builder if he assembled everything. Probably not likely but possible.
Yea if its reasonable it would save my time, ect then I will