Indeed, both word orders are fine, although it is more common to put the adjective second.
But beware that the two words you have don't have exactly the same meaning as "perfect body" nor do they necessarily make an idiomatic translation:
Perfectum is really a participle meaning quite literally "thoroughly done" and often means "complete" or "finished" but also "excellent" and "perfect" by extension.
If this nuance is fine, you can go with it.
But there are other options like optimum (best, best possible) and integrum (untouched, undiminished, not worn) and consummatum (brought to the highest degree).
The perfect translation of "perfect" depends on the kind of perfection.
Corpus can be "body", but it can also stand for "corpse" or "object".
It can work, but it can also be misinterpreted.
The only better option that comes to mind is forma, literally "shape", and I would probably use that to describe a beautiful human body.
The best translation depends on what you are after, exactly.
Your choice sounds pretty mechanical in flavor.
When Frankenstein finishes building his monster, he could well exclaim corpus perfectum! to declare the completion of the beast.
It could conceivably mean "perfect body" as well, but that would not be my first interpretation without context.
In the context of building muscle through nutrition and exercise the task is much more specific.
Instead of "body", I would go with something more specific in Latin.
Latin doesn't have a good word for a muscle.
The typical word is musculus, but it also means other things like a little mouse, so it is prone to rather hilarious misinterpretation as a brand name.
The two words that come to my mind are fortitudo (strength, force) and firmitudo (firmness, durability, strength).
I suppose the second one is more apt.
My suggestion is firmitudo consummata, which could be verbosely translated as "firmness, durability and strength brought to full potential".
If I understand the goal well, this should be of the right tone.