Grand Funk...

[blues_n_cues]

Stock....Buddy.... Who are you kidding? You will never buy an amp. You'll just get stoned and leave it somwhere in the bushes. Borrow a marshall lead 12 from somebody and It'll get you all the grand funk you want.

 

[stock_hippie]

I found my Marshall Lead 12...I rely thought I lost it..

 

[stephendarskin]

love that grand funk tone! trying to replicate it as well. was having a hard time getting the mids to match, but I'm doing better now.

 

[CRobbins]

I saw GFR at the Forum in Los Angeles many years ago.

 

[tubes]

thanks...guys...but what Marshall Amp should i use or get to sound like GFR...?

Cheers hippie.
I think it doesn't work like that.
I don't know for sure.
But I suppose that when emulating the overall sound and sensibility of another group it's more important to get a grip on their sensibility than on the specific gear.

Speaking as a hack who is always trying to fit in with different genres I would say:
Which amp?
Any good quality amp. Then tweak.