1; I would like to keep the DC servos and encoders
I think this is always a good start, everything is sized and mounted and get you down the road faster. DC power supply is already 'right-sized' too. Only caveat is they are likely 10 Vdc analog cards. Hardware choices if going Mach3/4 is lower. (Not too mention lifespan and differences between Mach3 and Mach4 and pug-ins for 4 is a bit of an unknown right now). LinuxCNC you will have a few options for hardware interface, Mesa, PicoSystems, and (new to me) General Mechatronics.

2; I have been looking at the Viper 200F drives (24 volt dc), Good choice and support if going Mach3 or 4(?), it is a Step/Dir command drive. Could use LinuxCNC, but somewhat defeats the capability within LinuxCNC of closing the loop back to the controller. May need to see if Hurco power supply will work or not, may need to reconfigure or replace.

3; Mesa 7i25 ? The 7I25 is likely too small for your servos. Likely the 7i40H (high power) will be better suited. I've never used, maybe someone can report. You might have to reconfigure or build a different power supply.

4; 5 hp VFD not sure which one yet I have been watching eday to see what they are going for and looking at new as well
I've never seen or used first hand, but I suspect that is the Hurco Parajust drive in the left or driver's side cabinet. Contact MartinCNC on how you can run this drive single phase for the spindle. However, popular opinion is to dump this finicky antique and get a newer drive. Probably the most expensive single component, if that matters.

5; For the programing Linux ? BOB or Mach3 I am not sure about the Mach3 but it seems most beginners start there
Many many people are well indoctrinated into use of MicroSoft Windows, this makes Mach3 a common and comfortable path. It is capable and low cost if you dread the Linux adventure.

6; I will try to reuse some of the existing stuff in my cabinet like the DC transformer contactors for certain functions etc.
I need some input I am ready to start purchasing my needs to get stared putting it back together again.
and would like to know what else I need to add to the list.[/QUOTE]
As mentioned above, if you change out the drives there is a very good chance you'll need to make some changes or replace the DC power supply. Also, depending on your hardware interface, you will have to see how straight forward it will 'plug' into your relays and solenoids due to voltage and amperage capability and I/O type. Additional conditioning boards or swapping out devices and adding or changing power supplies.