Speedometer off...

If the speedometer reads 1% high, go to a gear 1% bigger to make it more accurate. Reading 10% high, use a 10% bigger gear. Etc... You're saying 45 mph indicated at 35 mph actual, so that's 45/35=1.286 (or 128.6%). So, 33 tooth x 1.286 = 42 tooth approximately. (I think you have a 4.10 rear gear!)