Are there different lengths.I just got one that has the emergency brake drum on it.How do I make it work in a 78 stepside.How do I get a slip yoke without tearing the tranny apart.Is there a conversion slip yoke?

IIRC, the one with parking brake is not going to have a "park" on the 727 VB rooster comb thus the parking brake on the tail shaft.

there is another 727 with short shaft bolt on yoke that is for a large chassis and has a trans mount further back and bolt spacing wider.

the smaller RV chassis 727 short shaft with bolt on yoke has the same trams mount location/bolt spacing and can be used in cars/trucks with a drive shaft change to a splined slip yoke.

what you have will need a tear down with tail housing/output shaft change and a parking pawl rod installed (maybe a VB change?)

if you put it in the truck with the parking drum you just need to chop up a drive shaft and add the correct size spline/slip yoke like the bolt on yoke trans use.

then figure out the shifter hook up or trans plant the dash shifter.

what size u-joint is on it?

large 1330 3 5/8" across the cups?

they do have a baster joint that goes 1330 to 7260 so any mopar truck 4x4 spline/yoke could be used on the shaft and a baster joint at the park drum/yoke

Mopar used three different HD727 in pickup trucks, vans and class A,B and C motorhome chassis.
All of them I have had have park, including the ones for the heavier Class A motorhome chassis with the E brake assembly on the tail shafts
I have all three BB HD types 727 in my shop now including the HD pick up long shaft 727 that have the snap ring removable cover on the sides of the tail shafts instead of under the tranny mounts like the standard 727 have

I also have the shorter RV trans with the bolt on yoke.Have you ever used one in a truck.If so do you have any pics of the slip joint driveshaft you used.