The Alpha Sprint Special (can't remember how to spell the full name lol) is another great drifter...one of my favorite cars of all time.
Most of the classic JDM cars are pretty good too, for having low power. Both of the old Skyline GTRs are awesome, and so are the old Fairlady Zs (240Z and 280Z). Although its a little slow, one of my personal favorites is the Fairlady 510 (same thing as a Datsun 510).
And if you're talking about "older cars" that make good drifter, you have to include the Corvette Stingray, and more so than that, the Mach 1 Mustang...this car is certainly among the top drift cars in GT5 (with the right tune, and with the right driver of course)