Do you belong to Maserati Club International? They are the largest Maserati parts house in the USA. Incredilbe knowledge and very willing to help.
Give Kerry or Stuart a call at (253) 833-2598 and they can give you the spec's you are looking for.
Here is a list from their website of all the manuals they carry for the Series 1 Quattroporte:
QUATTROPORTE I
A Spare Parts Manual Ref. 230 $65
B Spare Parts supplement Series II & 107/A Ref. 231 $25
C Owner/Operator Manual for Series I Ref. 228 $65
D Owner/Operator Manual for Series II (from car 1412)Ref. 229 $65
E Information Manual, in Italian. Lots of good specifications, if you can understand some Italian. For Series I Ref. 227 $65
F Maintenance Manual; excellent information, but in Italian Ref. 226 $65
G Borg Warner Automatic Transmission in English. Service Manual for Maseratis equipped with the BW Auto Trans - very complete. Ref. 248 $65
H Salisbury Hypoid Axles in English. Service Manuals for Maseratis: 3500 GT, Mistral, Ghibli, Mexico, QPorte, Indy. Ref. 249 $65
Hope that helps,