I think 60 months is the longest they will extend credit on any car loan. I recently purchased a '01 GS300 with a 5 yr note at 5.5% interest and my payments are at $456 (this includes a 4 yr dealer warranty that covers just about any mechanical issue that might arise)
go to any car website (cars.com; edmunds.com; autotrader.com; etc.) and they will give you a loan calculator for you to figure you monthly payment. However, if you want payments at $370/month, you will have a hard time finding a 01 GS430 in that price range. Most of them start in the low $20,000 range, and a 5 yr note at 5.5% interest will start you around $430/month
My thoughts are after 36 months or so, the value of my car will exceed the value of my loan, so if you want to hold the car for more than 3 years, you should come out ahead when you sell it.
By the way, the Lexus GS models rock. I am thoroughly enjoying mine