I don't know how original or new this is but I do know that it is inexpensive and easy to do.
I spent this past weekend getting my RB25 to fit into my '73 240Z. I should be a little more specific. My RB25DET is out of the R34 Skyline chassis, 1998-2001 is my best guess, it has the coil packs on top of the spark plugs instead of in the rear if the engine. My motor came with the original Skyline mounts which are round and have two bolts to connect to the crossmember. The car is a 1973 240Z, I have the transmission mount with bushings and horizontal bolts that bolt it in place.
That being said, I lowered the angle of the original 240Z mounts on the crossmember by taking a little over 1 inch off of the outter edge of both mounts. The black mark in the pictures shows where I cut the mounts. This allowed for an angle that matches the angle of the actual motor mounts. I tack welded a new piece of steel on the mounts and drilled bolt holes for the motor mounts.
The transmission was just as easy. I had to cut off half, the front half, of the bracket on the inside of the transmission hump to clear the RB transmission. I them made two new brackets and cut a slot in the side of the transmission hump to allow me to place the new brackets 2.5 inches behind the original crossmember mount. I wedled the brackets in place and bolted the original transmission crossmember in place using the original bolts and original transmission mount.
The whole job took just over 1 day and cost me less then $20 to complete.
http://album.hybridz.org/showgallery.php?cat=500&ppuser=13334