it may not be that easy to get the info. towing something once or twice is alot different than a bunch of times. the problem with your k5 is wheel base, the longer the trailer the more of an issue it will be. i would tow a trailer probably to 30ft once but if its not that far but it wont be fun i wouldnt do it on a windy day. if your talking about reliable safe towing anything over 28ft is usually 3/4 full size truck territory. also the older the trailer the heavier they were, my parents had a 70'* 24ft and its heavier than the 30'* of today.
1998 Bonneville SSE
2007 Monte Carlo LT-KYB, Clarion, Polk audio, Kicker
1999 Yukon SLE-KYB, Air lift, Reese dual-cam, Tekonsha
1987 Firebird-355/th400-nothing stock