they are either 46mm or 48mm ...I forget which at the moment, I'll go check
The 3.5L upper plenum is not a very good option on the 3.3L, you just cant blend the two together within a reasonable thickness adapter. Mine was 3/8" and that was hitting the hood. I'm sure it could be done if you had something closer to 1" but you would definitely need a bulge in the hood. However on the 3.5L its a very impressive intake. On a 3.3L you are better off porting and tuning the stock manifolds or upgrading to the minivan intakes which Can fit with some coaxing and hood cutting. The van intakes give a very noticeable bump in torque which can be a lot of fun.