Lucky for all of us, most parts for any year of Vulcan 750 will fit other years. The only minor exceptions like there was a brake master cylinder change, little things like that.
A6 would mean the 6th year of production (starting with 1985 - which was a 700 in the US).
The exhaust has not changed since the bike was initially produced, so that right exhaust muffler will fit, no problem.
1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Rebuilt Forks w/ Progressive Springs
VN750.com Grill Cover
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R
1990 Kawasaki Vulcan 750
1998 Honda VFR800 FI
2014 Honda VFR800F
1989 Pontiac Firebird Formula 350