348 360 Modular Wheel Fitment

I just purchased 360 modular wheels to put on my 94 348 Spider. I know this has been done by others and I'm hoping to get the right formula for fitting the back wheels so the car doesn't look like a jacked up 69 Charger, not that there is anything wrong with those.
How much needs to be machined off the hub?
What wheel bolt length?
What tire size?
The tires on the rear rims currently is 275/40/18
I have spent a ton of time using "search" and really never found a true formula. Lots of inspiring pics and a few WTF's that make me really want to get this right.

Thanks!

 

Thank you for the replies. My wheels were delivered yesterday and are awesome. Unfortunately I will be selling them as I cannot see how to make these work. I've been all over the old threads via search and have seen plenty of pics of 348's with the modulars including 97 Spider's car which was one of my inspirations. My wheels came with like new 275/40/18 Michelins which I figured might be a bit big but had no idea until I did the test fit. That sidewall is HUGE! I have small hands and couldn't get a finger between the tire and the front of the wheel arch. that's way to close for my comfort and to be honest looks weird as hell. They also stuck out too far for my taste. My wheel shop here in Tempe who on any day could have an F40 or a Pagani in there is the go to place but they said no way is it possible to take off 17mm from the hub. There just isn't enough material. We obviously discussed different tire options but at this point I'm a bit demoralized and over it. Better to sell them and move on. Or, sell the Spider and get a 360 to put them on. LOL!

 

Not lowered at all. Stock as the day delivered. Damn your car looks killer.

 

This is what I'm having trouble with. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

 

I want to know what am I missing? Wheel Specialists wont do the machining as the say there is not enough hub. I'm at a loss here. I thought this was going to be easy peasy, machine the backs, put some new rubber on and be on my way.

 

I think before I throw in the towel on these I will do some tire fitting at Wheel Specialists. The person I got these from, "carbonsmith" here on F Chat is pretty sure changing the tires would get it sorted out as well. He also thinks some material can be taken from the hub. He has been fantastic to deal with from my first inquiry about the rims, the purchase, shipping(from Halifax) and now the fitment. Seems He's as determined to see these on the car as I am. Hopefully I'll be able to post results and pics soon.

 

Image Unavailable, Please Login Here's a little update to the thread. I dropped the wheels off to Wheel Specialists yesterday to start the machining process. After visually inspecting the wheels it was determined it could be done but not at 17mm as their personal margin of safety will only let them go 15mm max. After doing the math and playing with some neat little phone apps for wheel/tire fitment I decided to take off 12mm. By going with 12mm the new rear wheels outer rim will stick out 5.7mm further than the stock rear wheel. This should give it an aggressive widened stance to compliment the widened stance of the front wheels which will be 1mm wider than a 355. I decided to go with 215/45/18 size tires on the front and 265/40/18 size tires on the rear. Of course some of this can change after the first fitment of the rears as we may need to go 15mm shaved which will make the new wheel stick out 2.7mm further than stock. Here's a shot of it mocked up in my garage. I do love the look of these wheels on the car.

 

Ya there are several tire options we're working with. When those first pics were taken the care hadn't settled on the lift. When it did the gap got better but not enough to make me happy. Also by bringing the wheels inboard with the shave the meaty part should be back beyond it. I've looked at a lot of 355's and they're pretty close with the stock 265/40/18 so that's kinda the goal here. It's going to be a trial and error, hopefully not too much error. Definitely been an educational experience. I now know more about wheel offset and sizing than before. My guy at Wheel Specialists says I'm too anal and need to put the calculator down, it'll be all good. LOL!!

 

All done and quite happy with the results. 12mm is the magic number for cutting the rear wheels. I'm rolling on some ugly aftermarket wheel bolts until I can source some Ferrari bolts for the rear.
Here's a few pics while testing in my neighborhood. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login