ACE in Sandy has a great selection. I’ll get it Saturday morning.They don't have to be grade 8's but it's nice to have the strength. The ubolts are what really hold the packs together in operation when torqued to the axle. I like choosing a center bolt size that is tight in the spring holes. They can be longer and cut short if you have challenges finding the right length.
Thanks.Alpine fir? my favorite as well.
Axles looking well sorted!