I thought it was brought up one time here about the six cylinder cars having a different shaped engine compartment that made it hard to put a V-8 in them,,was this true or am I thinking of a different car?

Probally not on the 1955 models as that was the first year, I think anyways, that Plymouth offered the Poly V8. Before that, 1953 and earlier, they where a real pain to install a V8 in without moving the steering colum and other nasty things like that. I believe 1954 was the first year Dodge offered the small Red Ram Hemi, I really don't know what Plymouth offered that year
I'm almost sure that one of the members on here has a 1955 or 1956 Plymouth Fury with a B or RB motor in it, maybe he will pitch in for you about it

I have a '55 Belvedere that originally was a 6cyl with a 3 spd. I have not noticed any major differences in the inner fender shapes, or the firewall and components. Not to say I am right though - I am putting a 354 Hemi in mine, and it is a gasser-type build. So, I'm not using the inner fenders or other none sense.

Ok maybe it was the ones older than a 55 were harder to V-8,thanx

it was a 55 belvedere (the one I saw)

1955 Plymouth all have the same engine bay 6 cylinder or V8 are the same in 55 pretty easy to install small block mopar in them since they came with them ... there is a guy on here he had a 440 in his 56 Plymouth not a bad swap but all my 55's have same engine bay ....

Thanx guys, I found one that looked like it would be fun but I think the guy is either smoking weed or crack cuz I'm trying to line up a time to see and he flakes out like a typical craigslister

Look at it closely for rust. There are some patch panels that can be bought - like rockers, lower quarters (behind wheel), and some patch panels for the fenders. Not cheap though.

There are alot of "overlapping seams" in the panels of these cars. This means lots of places for moisture to collect and rust. Floor boards, rockers, body mounts, etc.

Doors and fenders are hard to find - make sure they are usable if you can.