I installed a remanufactured 302 in my 72 grabber. the numbers say it is a 1974 unit, i bought a new 28 oz. flexplate and 28 oz. fluid damper. in between 2000 & 3500 rpm it will shudder the car really bad. i had this problem with the other engine, but i installed a new converter and had to use a different flexplate when the problem began. could it be the converter itself ? please help, i miss driving my grabber. thanks !