The thing You can cut away and then add steel to change that crossmember shape without removing the complete crossmember.
The thing with any bolt in thing is that with a ladder bar frame things can twist easily. The engine crossmember is the largest factor in lessening that twisting.
Any universal thing is going to have some play in it and wont be a full on bolt in deal.
If you want a tube crossmember then brace in front and the rear ofyhe crossmember. Check all your frame measurements. Now double check them. Now cut out the crossmember, and build a tube version.
Gussets are your friend.
The factory crossmember is very tough and I would cut and weld in pieces to clearence before building a complete one. The exception would be if the frame was also tube etc.