The RealOEM catalog should have the bolt sizes and lengths for the air box hold down bolts.
By the way, in case you haven't figured it out you'll need a set of the #3 O-rings as well.
6, not listed, but i have the size and have guestamated the length.

No. Description Supplement Qty From Up To Part Number Price Notes
01 AIR CLEANER HOUSING BOTTOM 1 13721460339 $18.02 +core
02 Bump stop 3 17111460400 $1.19
04 Rubber grommet 2 61131243744 $2.80
09 Air filter element 1 13721460337 $52.25
11 INTAKE MANIFOLD 1 13721464559 $39.39
12 Washer 5,3 2 07119936416 $0.40
13 Hex bolt M5X10 2 07119913218 $0.12
14 Spring 3 13721460488 $12.05
15 IDLE REGULATING VALVE 1 13621461425 $153.71 +core
Yea, I had 3s on the original order.