ALWAYS run synthetic. I have over 150,000 miles on my MR2 Turbo (a car that puts out just over 100hp/liter) and have no engine wear problems. When we did my valve adjustment at 100k only one tappet needed to be adjusted. All of the others were well within their range. I'll probably get another 100,000 out of it before I need to rebuild it. I run Mobil1 15w-50. But, now that that's no longer available I'll probably go with the replacement Mobil 1 Extended Performance 15w-50( https://www.mobiloil.com/USA-English...ce_15W-50.aspx ) and just keep my oil changes at 3,000 miles regardless if Mobil say's I could go to 15,000 before having to do it.
Any of the Mobil 1 products will do you fine. Although I think I'd stay away from the Zero weight oils. Those are made for modern cars that have much tighter tolerances in the engine than your 28 year old Ferrari!
Use the highest octane pump gas you can get. Predetonation (knock) kills more engines than any other cause. Also the Chevron Techron additive works. I'd recommend their premium gas (as it already has the additive in it). If you don't have a station near you can pick up a four pack of the stuff at any COSTCO for about $10. Use it every fourth fill up. It'll keep deposits off of your engine internals and help keep those carbs flowing clean.
I don't think you need a lead additive. I'd had two 240Z(s) one (a 1973)during the change over from lead to unleaded during the 80s and then the other (a 1970) in the early 90s. Never had a problem running unleaded. Just make sure your using a high octane rating.