I am trying to get everything in order before starting to install my 6. How do I know how high on the firewall I am supposed to install the mount? Any guidance?

I have installed one and if you pm me I will try to answer your questions. I am out of town and won't be able to send you photos until Monday

Not sure, but I imagine the bottom point sits on the seam lip. You also need to find center on the car and mount.
Before welding in in I'd attach the engine/tranny and trial fit it to see if the engine is sitting right to the seals. You can drop it about an inch if you are having clearance issues with the decklid.

Before welding mine (RJ mount, same concept, different vendor), we did a test fit first before we committed to welding the firewall mount.

Mine is a Johnson unit... instead of a pre-install, I measured everything to see where I wanted it and decided to weld it as low as it will go - the bottom is right at the seam lip of the pan. The 3.6 intake is pretty tall, so I'm glad I welded it there.

I have used two of his mounts.

For CIS motors, I set the mount at 6 1/2" above the body seam.

For carbs / MFI I set the mount at 7" above the body seam.

I correct in assuming that we are talking about mounting the TOP of the mount at 7"? It seems obvious that is what you are saying however I want to make sure.

What rubber mounts are you using?
The ones on maddogs site look like sporto's which are a hell of a lot shorter and harder than the OEM 911 engine mounts. This can make a major difference in your install height.
It would be easy enough to add washers to make up for the sporto shortness but you couldn't go the other way around.

I find the sporto's very hard and they could transmit more noise and vibration compared to the stock OEM mount. I going to try stock mounts on front and sporto's on the rear (trans).

Edit it's not as much as I thought, around a 1/4". I'd add a thick 1/4" washer between the rubber mount and crossbar.
BTW adding a few washers between the rubber mount and crossbar would make it a bit adjustable in case you were slightly cocked off level or a bit high.

Yes ...........

The dimension of 7" came from Rich Johnson & his mount, of which I have used 3 of his.

BTW I know all this because I just made my mount this weekend, I believe the plans were copied off a RJ 1st generation mount.

I did a few modifications to the plans, mostly to clear stuff like the wiring. One thing is I never looked at the present RJ or MD mounts, this one I made is a lot heavier/stout.

Are there no mounting instructions from Maddog?

First one done in 2007. Car was a '70 that I put a 2.4L into. Note: I didn't say I could weld, but I stuck it!!!! Ground a bit of metal here and there to get the fit I wanted.

All I saw as far as mounting instructions was to bolt the mount in as a trial fit then weld away after the trial.

Here are the mounts that I got with the kit. Are the stock or sport?

They look like sports to me. I use them without regard to their depth.

I never bolted the engine mount in in any of the cars I have done. Marked off where the mount should be (center line of car & height I wanted it) and then tacked it in place. Went back over as I was satisfied and splattered the rest of the welds.

Here you go... Instructions are on his site.

http://www.maddogsmotorsports.org/INSTRUCTIONS.html

Oops

We did a test fit first to get the exact location for the mount:





Then welded in the mount:

I am on someone else's computer (MAC) and I have no idea how to copy into a thread but you can find my thread by doing a search "maddog +mount" and search by jeffs9146 posts only. You will find a complete thread with me going through all the same questions you are asking.