I've use the Lokar cables to make throttle cables on Z's for SU's and Triple carbs for years. I'm in the midst of doing on my 510 project as well with a similar SU setup, but I haven't really started it yet, so I'm not sure how some of my assumptions work on 510's. Overal layout of things look very similar. Here is what I've learned from doing all the Z's. I'm sure most of it applies.
1.
Regarding the ball on the pedal arm, yes, remove it and use the lokar ball in its place. Your challenge in this area is mounting the cable to the firewall. The issue is the distance from the firewall to the pedal ball when it is at its closest point to the firewall (no throttle). That long end on the Lokar cable that snaps onto the ball is way too long.
There are three approaches.
-Shorten the end but that might mean some welding or fabrication.
-Create a mounting block to cover the firewall hole that has a thickness sufficient to move the mount point into the engine bay enough so that the end link is spaced correctly from the pedal. I've made about a 1" thick AL block with a 9/16 or 5/8 hole now quite all the way thru the back to accept the cable mount nut, and two small through holes top and bottom to screw the block to the firewall above and below the existing hole.
-Buy a different snap on ball end and make your own from Midwest control products
http://www.midwestcontrol.com. These guys have the metric ball studs that identical to the stock Nissan ones, and their mating snap on female ends in several styles. The BSM-5-C is the 8mm ball stud and I've used the DMCBH-5 and QM5 mating ball ends soldered on to the end of the Lokar cable. That way you get a real short end so you can use simple washers at the firewall to mount the cable end. Lots of other cool linkage and cable fab stuff with these guys too.
2.
Linkage the carb, seems like you're on the right track. That piece does seem to have a bit of quadrant/radius to it, just hard to see inside that slot. Mostly make sure the cable is tangential to the linkage arm through the majority of the travel. I'm a bit nervous with that cable mount making the cable come from the top like that. Will the cable arc above the manifold rub the hood? Have to keep th
3.
What setup you use, ensure that cable at the pedal and carb ends go as straight into the cable sheath through most of the travel and it's typical-use range or risk wearing a groove in the sheath lining and eventually key-seating/jambing the cable in the sheath. No fun if you're in the middle of passing someone at 100+..... Lokar does not suggest any sort of lube, but like wheel bearing grease, I'm not sure you can put too much lube in there... This also becomes part of the yearly maintenance and inspection routine right?
I'll post up some pics if I can find some of what I've done in the past.
