I just finished the swap of the 727 to an A518 on my '74 fury, went out for a test drive and realized that the oil pan of the A518 is just too big and hits on every speed reductor.

Could be any problem If I swap it to the oil pan of the 727? The 727's oil pan is considerably little compared with the A518

I'm running 3/8" cooling lines with independent tranny cooler

 

no. They won't swap.
The 518 has added valve body section for O.D. / L.U.
with that being said. How did u mount the trany.?
what mod.s did u do?
do you have it stuffed up in the well enough?
You should have clearance...is it a oem pan?

 

I used the stock tranny crossmember to mount the transmission, just did a few mods on it to have enough clearance for tranny tail but the transmission is all the way in the car, even the clearance between tranny and car floor is almost nothing, something like 1/2" to 1"

The tranny pan is the stock one, this tranny came out of a 97 Dodge Ram so I don't know if maybe truck trannys has a deeper pan

Right now the clearance between floor and tranny pan I think is no more than 5"

 

This a very interesting mod. With alot of details.
Ive got the same mod in my 87 5th ave.
I have photos posted here at the forum i will have to look up the actual post as i dont remember the name.
I had to chop the cross member and manufacture a new one. And cut the floor back all this to fit the O.D. Module.
It's absolutly larger than the 727 tail shaft.
Sooo with all that typed.....lets see some pics if u got em

 

Has the car been lowered ? I have run a 518 pan on a 727 No clearance problems so I would bet your mounting is not up high enough