Thank you for contacting me direct. Since I do not use this site like others, I'm not constantly checking in.
As I had guessed, it is a 2.5 way series network. And, as I had mentioned, your plan to mount the front three on their sides is flawed due to their intended dispersion.
Any attempt to convert them to a MTM is flawed because the two 4" drivers are different, so removing the large coil, and reducing the value of the smaller coil is not recommended.
You could try adjusting the toe in/out on the L/R for best results (prior to modification). The L/R would need to be mirror imaged whether mids were in or out. However, I just have a hard time seeing the center working out. The angled face plate will likely be working against you as well.
If the front three were mounted vertical, I would still need a description of what you felt lacking before making parts recommendations. The electrolytic would have to be replaced, but an air core replacement for the small coil would depend.