It will be a lot easier to do without the front clip on.

First thing to know is that I am a professional accountant, I don't even qualify for a backyard mechanic as I have only ever swapped out 4 engines and three transmissions. Two LeMans a 350 and 454, one Mustang 302 C4 and a 5 speed and one Fleetwood 500 THM 400. The Cadillac was the only one without a clip and it was by far the easiest to do because of access and ease of getting at all the places and bolts you needed. The Mustang was a real pain and required constantly removing one more cross member and one more of whatever was in the way. The LeMans were a snap even with clip on the car. 

Do it with no clip if possible. Much easier to access, less chance of damaging sheet metal, can double check all your bolts by eye and save your knuckles and back a lot of pain. I'm talking from a lot of years ago when changing engines and/ or transmission was a weekly or monthly exercise.

I'm sure you know a 1965-1970 B body BBC requires specific components, oil pan etc.

Was the car previously a big block with a T-400 ?? If not it will require trans cross member tabs to be welded to the frame.

Nice project !!

Thanks
Randy

I'm kind of late to this thread but I have stuck the 396 back in my 66 Grande with the front  clip off and put it on later.  Works best in my opinion as you can rig up a rad and get everything tuned up and shipshape before you put the clip back on.  That way you avoid a lot of back pain trying to access stuff over the fenders (not to mention avoiding damge to them.)

As for the 400 install i have a another 66 with the stock 396 and TH 400.  They are longer than the powergide so they have the crossmember mounted further back.  Not hard to do. as previously stated it just took a couple of extra frame tabs form the factory to accomadate it. To stick the tranny in my 66 Grande setup with the TH700r4 which is also longer than the PG we just bent the crossmember a bit back and spaced it a bit down.  Worked really well.

 

 

Also if you think your car was a big block you should check for the extra rear top swing arm (283 cars only had one) and the 3/8'" fuel line.  It won't be definative but it will tell you if you car had more than the standard 283 PG combo.

Sending the VIN to George Zapora will be the way to get some real info. We'd all like to know as a big block Grande (or Pontiacs for that matter) were pretty few and far between.

I've never removed a clip to remove or install an engine w/trans. Just have to tilt and roll it in carefully. An extra pair of hands would make the job go easy. I keep a spare transmission yoke around and insert it for the install. Tilting the engine and trans to get it in there will send a good bit of fluid out the tail shaft.
Actually taking the clip off would make things easier, unless this is the only reason to remove it. Seems like a lot of work for little gain and leaving it on avoids the possibility of damaging parts that you really don't have to remove.
Also, if the car is on the ground it's a lot easier to roll it than to try and make fine movements with a portable hoist (or skid-steer) and all that weight suspended over you and your helper.

True enough. I had my front clip off to fix rust etc so i had disassembled the whole thing in any case.