Slant dies when put in gear.

First check the two simplest things. Your timing and vacuum. You should be anywhere around 5*-10* BTDC with the timing (make sure it doesn't ping if you go too far with it) and your vacuum gauge should read 18-21 or so. You can get away with 17 on the vacuum but anything below that and you'll start running into problems when the car goes into gear and drops the rpms.