BikeMasters brand Clutch PN is 07-0572. Brake is 07-0566. I just replaced mine yesterday with black levers. I go to a Motorcycle Access. shop in Mesa AZ and the owner is awesome. First he found the stock levers then matched them up to dirt bike levers.
Edit: forgot this is for my 95 so make sure they are same on your 88.
Clutch lever is the same, brake lever is different. Bikemaster doesn't show a brake lever for the '86-90; they do show the clutch lever as 07-0572 for the '85 700 LTD, and the brake lever as 07-0563. They also show a different clutch lever for the '86 up 750.
VN700A LTD 1985 07-0563 B 9.99 07-0572 B 9.99
VN750A Vulcan 750 86-90 07-1294 P 10.99
VN750A Vulcan 750 91-06 07-1297 P 9.99 07-1294 P 10.99
The "B" means Black, the "P" means polished; first number (07-0563) is the brake, second in the same line is the clutch lever
I'd think that if the -0572 fits your '95, and Bikemaster shows the -1294, then the VN700 levers oughta fit his '88, but I wouldn't swear to it; I'm half tempted to order a set for the '87 just to see if they will.
The 07-0566 shows to fit a Ninja 600, among others, so who can really tell what might fit what? Without someplace like that Motorcycle Access. shop to compare 'em in person, it could be a crapshoot. We've got Cycle Gear down here, but I dunno if they carry Bikemaster levers, offhand.