5.0 did a test on these headers.Not that i belive magazine articles but it shows them installing them with the kmember in place.
These picked up 5~7rwhp on the top end and 8~11ft lb of torque on the top end.But lost a few down low(below 4k)
As far as install longtubes or shorties do NOT need to drop the kmember .Its a option.Ive done both installs. Shorties in about 2~3 hours.Longtubes in about 4.Thats using a lift and having all the tools needed.No dropping anthing besides a engine mount.
That settles it for me. If you have to do the same basic install for shortys than for long tubes, it amazes me they sell any shortys at all. I'd still like to see a dyno of an equal length shorty to see the difference. Thanks for the info.