right exhaust manifold

[okie6801]

I bought a set of manifolds from summit to replace a set of cheap headers. this was the only style they listed for my 71. http://www.summitracing.com/parts/rn...del/c10-pickup

the muffler shop is telling me its not the correct one for the truck because it routes the pipe up against the starter. they say the left should dump out the rear and the right should dump straight down. Is this true?

these would route pipe by starter on any sbc application so I don't see why they won't work on my truck.

i'm not wanting to buy another manifold and have a mismatch set.
any input appreciated