First swap help.
 

Ok I have a 70 Chevelle I just mocked up my ls with a 4l60e. I'm using energy suspension motor and trans mounts with the new Holley pan the plates I'm useing put my set up close to stock bellhousing location the pass side head is about 1"3/4 away from firewall and I'm useing the stock 307 frame mounts the oil pan is about 1"1/4 or so off of cross member with the inner tie rod grease fittings just missing pan. I also used the stock crossmember Abe just cut off the tab and re welded it. I'm at 4 1/2 * down on motor and can't go up on trans anymore or it will hit. I am running ridetech level 2 coil overs front and rear there complete kit but it's not set up yet. I'm concerned about my driveline angle at 4 1/2* down???? So if anyone can give me any help or insite if that will work or what I should do to fix this? Thanks Tom

This is a topic that has as many OPINIONS as there are chassis builders. I'm about where you are angle wise in relation to the FLOOR of my shop, not my frame, which is raked.
I've read a hundred threads concerning this topic, and i've found so many different ideas or opinions on this topic. Me personally, I feel it boils down to the individual car, with intended usage, suspension setup, and power level.
Let five chassis builders chime in, and you'll likely get as many different theories.

Thanks Scott. You don't live to far from me I'm in canton just on the line of cumming.

We had the same issue plus power steering pump to box interference. we ended up cutting the trans tunnel, raised the cross member for more exhaust room and made our own frame stands.

this is very true. What i like to do is level the chassis out as per chilton specs then level out both engine and differential in relation to each other then try to control the differential for changes

The only way to get the trans up further to get you where you need to be is either cut and mod the tunnel or try using shorter motor mounts. I'm doing a t56 swap with short and wide motor mounts and cut the tunnel out. I got the trans to about 2* down. I need to make sure the slip yoke and drive shaft clear the tunnel now. Have you checked header clearance also?

I have the short wide mounts with energy mounts it is as low as I can go without the inner tie rods hitting pan so I'm cutting the tunnel and raising it up 2" so in the futer if I want to change to a 5 speed I have room. No problem with mid length headers

just an idea: you could lower engine down and notch the oil pan for tie rod clearance. A little easier than messing with the floor

I don't need to go up much on the trans yoke I'm at 4.3* now and I'm running the Holley 302-2 pan so if I can get the yoke up to 3* I'll be happy with that.