1956 engine changes include redesigned right crankcase allows oil to be  routed to the top end through an oil pump check valve.
cylinder heads now  have 9 fins on push rod side.
the  FLH gets a bigger cam with higher lift and shorter duration called the victory cam.
The oil tank gets a red v decal on both sides.

1956 sales brochure
1956 sales brochure

Here are some great sources for detailed information about Harley Davidson’s 1956 Panhead

How to restore your Harley-Davidson by Bruce Palmer 111

Riding vintage website

the Jocky Journal web forum

hydra-glide.com The panhead and flathead site

The Harley Davidson Panhead service manual 48-57 rigid

1956 models

modelengine typeactual displacementcompressionoptions
FL sport solo74 c.i.high compression73.66 c.i.7.25:1
FLF sport solo footshift74 c.i.high compression73.66 c.i.7.25:1F=foot shift
FLE sport solo traffic combination74 c.i.high compression73.66 c.i.7.25:1E=traffic comb.
FLEF sport solo traffic combination foot shift74 c.i.high compression73.66 c.i.7.25:1F=foot shift E=traffic comb.
FLH super sport solo74 c.i.high compression73.66 c.i.8.0:1
FLHF super sport solo foot shift74 c.i.high compression73.66 c.i.8.0:1F=footshift

NOTE: the ” F denoting foot shift will not be stamped in serial number.

1956 models available colors

paintstripesspeedometer
*blackWarner speedo is redesigned with italic “Day-Glo” green numbers and hash marks with gold painted center
*pepper red
*atomic blue
*champion yellow
P police white
P police silver
*flamboyant metallic green
white
pepper red/white tank panels
black/champion yellow tank panel
atomic blue/champion yellow tank panels
* flamboyant metallic green/white tank panels

*= extra charge

* =standard color could be ordered without tank panels at no extra charge.

P =police only

*black

1948 panhead black paint color

*pepper red

*atomic blue

*champion yellow

P police white

1948 panhead police white paint color

P police silver

1948 panhead police silver paint color

*flamboyant metallic green

white