You can get a tank from Ronco with no holes at all. That gives you the ability to cut your own holes where you want.Many of the tanks that I'm looking at have the openings on the side, not the top.
If you look at my photo, in the lower right is a plug fitting. I made the mistake of having them put threaded fittings in the same location as the original fittings. The problem was, if I used their fittings the elbows would stand out too high to fit in my space.
I considered a shorter tank with more frequent pump outs but hated the thought of that, and the thought of wasting the $250 tank I already had.
Ultimately I plugged the holes, turned the tank around, and used the fittings I described above.
Personally, I'd avoid side mounted fittings if possible. It will either reduce your effective capacity or allow waste to sit in the hoses if the level gets high enough.