Alignment will certainly play a big part, small issues are multiplied if caster, camber and or toe are not within spec. Depending on the extent of your modifications you might have to play with adjustments until it handles well.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy