axle I.D. countin'bolts and teeth

[5th_Ave_Sleeper]

I Know this isnt the correct forum to place this question, but it seems to be the place where all the brains hang out.
What is the external differences between a 7 1/4, and an 8 1/4 inch rearend? I found a 77 dodge van (long and heavy) that came equiped with a /6 and a 4sp OD tranny. is it safe to think that it would NOT be a 7 1/4".
My thoughts are that if it is a heavy veh. with a six cly and 4sp OD that mother mopar would have installed a somewhat healthy axle with a low gear ratio (maybe 3.55 or even 2.9somthing to one?
I would like to know if it is Not a 7 1/4" before I go counting ring and pinon teeth!
I've found that 8 1/4" are hard to come by on a budget. thanks for any help you can throw my way.
5th

[coach71]

Sorry don't know the answers myself, BIT try this see if it helps, http://members.xoom.com/dustermocar/techpage.htm

[69CORONET440]

What you are most likely looking at is a 12 bolt rearcover 9 1/4 rearend.These took the place of the 8 3/4 around `73.As far as the 8 1/4 "being hard to come by" hell i see them all the time.Here's an easy way to tell what your looking at in the wreckin yards: small 10 bolt rearcover 8 1/4 - 12 bolt rearcover 9 1/4 - LARGE 10 bolt rearcover 9 3/4 Dana60 - 14 bolt rearcover (looks like Dana60) GM Corp - don't forget to check the axels/bolt circle and drums- good huntin'

[PINK71T/A]

I had a 74 Dodge Stepside Original /6 Truck and it had
a 9 1/4 i think most Dodge Truck/Vans had at least the
9 1/4 rear axle (at least everyone ive seen has?)

[BillyBob]

In that year it could very well be an 8¼" rear w/10" brakes. Just count the cover bolts as suggested by the above members

[5th_Ave_Sleeper]

Thanks for the valuble info and links!!
Here are some additional thoughts on the subject.
I know it has 5 lug hubs,
I know it is not a dana or 8 3/4,
I know it does not have an I.D. tag,
Anything is better than a 7 1/4 right?
-->Heres what I DONT know;
is a 9 1/4 strong enough to handle @400hp/ 380ftlbs?
Gear ratios for said 9 1/4 rearends
Is a 8 1/4 strong enough for the above mentioned power?
Can I get low gears (@3.55) for an 8 1/4?