I converted the program to mm and it functioned OK.
If you check in the Photos there are some pics showing the Emco standard tool post on a C5 lathe. There are 2 types, 1 has a central dovetail to secure in the block and the other an offset dovetail, both blocks are the same size but obviously the tool holders are not interchangeable.
Size of the block is 55mm square and 40mm high, there are 2 ground Vee's to accurately locate the toolholder so tool offsets remain constant between changes.
The block is mounted by a single M12 skt cap bolt to a 10mm thick plate which measures 60x80mm that is secured to the crosslide using the same fixings as the Auto tool turret with 4 M5x16 setscrews.
For external threading I use a 12mm square Toolholder with replaceable tips but also have used carbide tipped tools on various size shanks.
For internal threads I use a selection of ground round section HSS for the smaller sizes, carbide tipped for larger and deeper bores., always try for the best rigid set-up and take very small cuts per pass, always use "springing cut" passes on internal threads as you do when boring.
The above statement is true for the Tool turret also, you can split any bushes you use to accommodate round tools in the turret socket, make sure the split is at 90 degrees to the tool securing screws before tightening then the split bush will clamp the tool securely. You may have to reduce the wall thickness on thick walled bushes by partly cutting lengthwise through the wall opposite the slit to allow closure.
Looks like you will have fun doing those fin cuts, .031" is going to be a delicate tool. All I can suggest is you grind the tools from square HSS stock leaving as much material below the tip as possible, grind the minimum length at .031" and only use a touch of clearance angles, top rake (7-10 deg ?) will help to form a nicely coiled swarf especially if kept lubricated. Set the tool at exact centre but if that doesn't work you may find better results with the tool a few thou below centre. Take some trial runs with the same material before putting your cylinders to the test, for starters infeed at 10mm/min using 200 rpm. Suggest you use G95 in case the tool jams, gives you the chance to manually back off.
Keep us informed reference feed rate and spindle speeds you finally use for cutting the fins.