im about to change the power steering fluid on my truck witch is a 1989 gmc r3500 with a 454 and was told by a friend that i should use atf?i was wanting to make sure before i do it should i use atf or power steering fluid?is there a benefit for using one or the other?

Use whatever is recommended in your owners manual,I normally use Delco power steering fluid in Gm pumps.
Keep in mind ATF could also be synthetic which the pump may not like. GM'* fluid work well & is long lasting.

Yeah use what the manual says. I tend to use the Prestone stuff from Walmart. It seems to work well.

In a bind, you can use transmission fluid, but there'* no great reason to. Also, I don't know what the new Dexrons would do or not do in a power steering system long term. Last time I did it was on a `70'* B-body with a saginaw power steering pump with a leaky pressure hose. It never had an issue. A few weeks later when I changed the pressure and return lines I flushed it out and put power steering fluid in.

Installing a new PS Pump? There is a break in period of 500 miles on GM pumps & no synthetics should be used during the break in period !!
Just a note regarding Dexron VI ATF -it is a synthetic fluid.

no it needs a new line old one is leaking so i thought since i will have most off the fluid out and would need to bleed it i might as well change the fluid since its been awhile and looks like it needs it

I'd say just use power steering fluid.