Cam & Converter Q's

OK i hav a MP 450/455 purple shaft in the 318 with a 3800 stall 727 the car runs at about 1300-1400 rpm in park as soon as i put her in gear she drops to a grand an dies,is it possible for the converter to be to big for the cam?the timing is right an the combo ran like a bat out of hell last year with a bigger cam in it now im thinking its to small for what i got Thanks
MIKE