my 78 dodge van slant 6 is leaking oil in rear of pass side head.
my friend said Bars leak might help. any truth to this or any other fix besides changing head gasket?

Heck not driving it would fix it too, in a van its all right there in front of you, id spend a afternoon and replace the head gasket if you determine thats the real problem.

for sure pin it down & a HG would necessitate a R&R.

Head gasket, valve cover gasket, several options. Spend some time and find the origin of the leak, By the way your friend's and idiot.

It may not be the headgasket Steve. More likely it is the rocker cover gasket. Clean the area up and check it closely. Pretty easy job in a van.

As for your friend. I wouldn't call him an idiot like ^ but no chemical additive will out perform new seal or gasket.

I'd save Bar's leak for I'm stuck in the desert with x amount of water and I have a radiator leak and don't want to die out here.

Yeah, Barr's Leak is for the cooling, (water), system and not for the lubricating, (oil) side of things, or at least I've never seen a Barr's leak product for oil.

i will clean it, and check before changing head gasket. and hoping you guys are right!

Yep, get it SUPER DUPER clean using engine degreaser and your local car wash you spray yourself. Once, it's clean, drive it for a day and the oil leak will be obvious. I'm betting a valve cover gasket...but check.