The posted basic 1440GT VFD install is pretty straight forward, I have made a few updates so send me your email and I can send the revised files. They are guidance documents as far as suggested wiring changes and programming parameters for the 1440GT with the WJ200 VFD, but you assume all risk/liability for any mods you make to the machine.
The lathe will operate the same as if it was on an RPC, but with the added features of controlled acceleration/ deceleration, braking, speed control, etc. The design is built around the WJ200-022SF sold by QMT, cheaper VFDs do not work well for the lathe nor support the input controls of the WJ200. I primarily use the Hitachi WJ200 and Yaskawa V1000 VFDs which are mid-price, support a wide range of programming features and have very good reliability. They also come with tech support (minimal) and a warranty. You can get an inexpensive (under $20) tachometer on eBay but will need a small 12VDC power supply to run it.
The basic 1440GT install strips out the motor high voltage wiring to the forward/reverse contactors and just uses a set of their contacts T1 to switch the VFD input for the particular forward/reverse command. Contactors are not ideal for low voltage (24VDC at around 10mA) used for the VFD signalling, but seem to be OK if the contactors are new. Using used contactors/rotary switches does not work. You do need an external braking resistor and you will need to replace the brake switch to a dual pole type, one side uses the existing wiring (NC) which goes open when the brake is applied and the other side (NO) sends a free run command to the VFD. Although there are variants on the internal wiring, those to the Forward/Reverse contactors does not change. I have seen them come with both single phase and 3 phase coolant pumps, last I saw they are single phase 220V so that needs to be checked if you plan on using it.
You will need to build a VFD enclosure, I have a guidance document as far as parts needed and some basic wiring schematics as to suggested connections. The VFD cabinet can be mounted behind the lathe on a wall or some people mount it to the outer side of the headstock cabinet. You need to meet all applicable electrical code requirements, so if you are unsure have an electrician check out you final wiring.
The 1440GT is a very nice lathe, so enjoy.
Mark