For 70s era stuff then GSi are hard to beat for old school electromechanical keys. They have both freeware and pay ware as well as some hardware like the Burn Leslie simulator. I used the VB3 simulator on this one take per track quickie recording last month.
https://soundcloud.com/rockstar_not/straight-back-to-the-seventies
A proper B3 player could do much more with the VB3. The synth is the freeware mimimogue va