Helping a friend install a 400 in an Aspen.
Details:
Slant six auto car.
slant six mounts were cut off K frame so now mounts could be fabbed and welded on. They are gone...
bolted up the 400 and a 727 and slid it under the car. The trans mount (spool type) was installed and the motor hung about 2 inches offset to right.
Then the K frame was slid under and bolted up.

The engine seems to be too far back (R valve cover against firewall), the steering doesn't clear the Milodon center sump pan, and the pan is also only ~3/4" from the K frame flange at the front right. I get the feeling that the pan will have to be changed, but the motor still seems too far back with the trans bolted up.

What have you used (headers, oil pan, trans mount) to install a BB?
It's too late to praise the Schumaker mounts, unless we can source anouther Aspen K frame and the mounts for free or close to it.

there was a Mopar Action issue that had the orange cover that had an several extensive articles on all aspects of that swap. Dont remember what yr/mo it was as I had it & sent it to someone (on here) who needed it. Dont know if they (MA) have archived articles or not but I would check as it was comprehensive

I started building a 77 RR years ago.
I had a 383/727 in it.
I used the Schumacher mounts, a set of B body headers.
I had to slice a small section of the pass fenderwell to clear the # 1 header tube
I used a C body pan that had the pinion notch in the pass side..
there was going to be a lil interference with the rag joint rubbing a header tube on the drivers side.
I was going the remedy this with a U joint in its place. (something like a Borgenson shaft).
The trans bolted in its normal place with no clearance problems anywhere..

What did your 400/727 come out of.?
It has been discovered that some 727s have a different tailhousing.
This housing sets everything back 2"..
I had a 65 B body 8 3/4 with 3400 SS springs and 275 60 15 MTs on the rear..

I have done 6 or 7 swaps in A and F bodys.
First if your trying to do this swap with stock parts to save money , you may have to do this;

remove the lip on the k member and leave just enough to reweld .
you really need a c body base pan (400 ci) to get good clearance

you may have to flatten out lip where firewall and floorpan are joined .
reverse the tranny mount so engine will move forward
depending on what type of mounts you used , some mods may be needed to let the engine move forward.
i used manifolds every time and only had a few clearance issues with the 440s
It should not be a hard installation with a b block .

I'll have to get confirmation since this is one guy's project, and lots of another guy's parts. I was just lending a hand.
I think it was the stock /6 trans crossmember and mount. the trans was marked '65 coronet' (the parts guy has one), but was not a cable or trunion, so I would assume it's a BB B body trans. He has had various engines in the Coronet. It's getting a nice stroked 426 Hemi soon.
The 400 had a set of headers installed. I think they were B body style. They fit pretty well but were tight around the steering box (no shaft yet).
The milodon pan seemed to be the big fitting issue aside from the rearward bias of the engine/trans.
It's the usual deal, trying to save money by using what's around. The parts guy has some neat stuff, more racing than stock.
The main thing will be getting the trans mounting set up so it's all set up to fit.
We looked at rotating the mount to move it forward, but the parts won't allow that. I'll get more info and maybe some pictures. Thanks guys.

Its not really that hard at all overall, but after putting a 440 in two f body cars and what a small block stroker can do makes one ask why??? Unless the BB is a stroker as well.

But if one is doing it all can be done with mopar parts and bolted in, and still keep the ac working on the car.

The biggest issue I ever had was I had to grind a lil bit of the drivers MM bracket on the k frame as the oil filter lip would touch it and every couple weeks id have to tighten up the filter.

I put a trouble free 7k miles on the 440 mag in the last one before selling it, ran a respectable 13.6.

I dont recall having hardly any issues then a tight fit...I will post some pics if it would help.

The car is being built as a low budget street/strip car, mainly for cruise nights.
The parts are what we have laying around, hence the 400 and auto (and Aspen).
I asked the parts guy and the trans is a B body, so are the headers as well as the oil pan (again, a deep sump Milodon).
The trans crossmember and mount are the /6.
Looks like this but with only one 'ear'
Mount will only bolt on the trans one way, and only fit into the crossmember one way. The tube section isn't as long, it's flush with the rubber and the rubber is solid urathane.