Astro Van VS Late Model Hydro boost unit

[BR3W CITY]

So I finally made it back into the garage and have my truck going for this season, and one of the top items on my list is finishing the hydroboost. I need to hit the junkyards this week, and located a few different hydroboost units.

Is there a fucntional difference or preferred unit for these conversions? I've seen the Astro Van units, and then the late model silverado hd hydroboost units, all around the same price.

I'm running an lq4 with the hydroboost-ready ps pump, and if it matters, the 72 steering gear.

Thanks.