1992 chevy 454 ss truck question.

[deportes]

My 80 yr old father in law has a 454ss truck with 60k miles on it. It suddenly started pulling to the right when you step on the brakes and it immediately comes back to the center, it gives a jerky uneasy feeling. He is concerned specially driving the truck in winter weather. I am not 100% sure what the problem could be, a contaminated brake pad on the left side, a bad caliper what do you guys think.

Thanks.