R31 is probly the most ideal, they have the shortest factory strut length at 400mm, you most likely wont need to shorten them compared to stupidly tall b310 struts.
R31 struts have a horrible disc hub setup though, the disc is part of the hub assembly NOT separate. R31 brakes are larger diameter than 910 and S110.
If youre lucky enough to get R31 turbo struts, they have a slipover disc to hub setup, and have 100mm caliper spacing so you can fit 4pot calipers!
910 struts are taller than B310 (checked as I was gonna use some 910 shocks in B310 struts, not gonna fit!), they have separate discs and hubs though.
S110 struts have solid discs?? If so, then they arent gonna be near as good as the above options.
S12 struts and brakes are identical to 910, so am pretty sure that S110 is solid disc.
Ive got a set of R31 struts, and incomplete 910 struts, will probly use the 910 set in my wagon as its an A15 daily.
If youre going out on on your B310, use the R31 struts, fit 910 hubs and slide on some S13 turbo 280mm discs and calipers with adapter plates
