hydraulic motor lathe turret, keep switches or switch to rotary encoder ?

Are the tachs mounted on the motors or on the screw ? Tachs should go to the drive, they are velocity feedback.
The four switch’s will represent a number based on which switch is actuated . Each switch will represent a weighted bit. From right to left.
True. False. Decimal
Switch one. 1. 0. 1
Two. 1. 0. 2
Three. 1. 0. 4
Four. 1. 0. 8

0110 = 6
1000=. 8
0011=. 3
Ect

Use wsum to convert the weighted bits to a decimal.

Tachs are mounted on the motors and directly connected to the Arcamatic drives.

I am using a 7i97 and a serial connected 7i76 for additional IO. I may grab a few of those other modules for use on the pendant controls, Mesa is out of 7i73 afaict

Seems like a 7i76 is a step and direction card. Your drives are gonna be analog. I wanna say you need a 7i77 for analog drives. I may be wrong about that...

I have a 7i73, brand new , never used. Sell it to you for what ever the going rate is. I use 7i84 for panels , I like the terminal blocks. 
 

the 7i97 will handle all of the analog 0-10v controls, the 7i76 is just there for IO, I already had it on hand and the machine I was going to use it on was scrapped after I gutted it for parts. I also have a set of steppers and stepper drivers and I might use them for things like pressure control etc later. I very well may put a stepper on the turret drive and remove the hydraulic motor, I doubt it, but I have options now.

I may use the 7i84, I do not need a lcd, I have a 24 inch touch screen monitor that's being put on the machine. I would however like to use the factory control panels with some changes.