A 1992 if you ask me, not that I have experience with arenacross.
Some friends and my race shop ride pre90( EVO in UK). Most of them ride 89 rm250 and they say the newer/ modern the better. Especially with suspension, so there for 92 would be best if you iask me. And if I'm correct the link was very progressive what would be good for this.
What I "know" about arenacross. Slide fork tube up, rear wheel as far forward and compression turned in some clicks and maybe one or two more teeth on the rear sprocket and lower rear subframe.
Dutchie