What exhaust can I run with a 1981 Formula 302 LS with twin TRS setup (Mercruiser transmissions, not Borg Warners)?

I am not quite sure about the risers or the overal best options within a budget but I came up with two options.

1. Get the 496 aluminum manifolds and ??? risers

or

2. Get the old Mercruiser./gil Hi-performance aluminum manfolds and ??? risers.

ANy help is appreciated.

My father runs imco powerflows on his 302, on 454s turned into 496s

Well I am trying to go on the cheap buying used manifolds (in good condition). Any info on the riser height?