that looks like it will do nicely! Just an idea, the 69 mustangs have plastic inner fender guards instead of the steel ones on yours and earlier mustangs, they have to be trimmed to fit but weigh almost nothing, also you can make the inner door hinge plates out of alunimum   Pound here pound there!

I was going to try the same thing 25/30 years ago, (before dynacorn), and discovered the same thing about the quarter lines It killed my project On my car Idid about the same things Mike did for tire clearence but I did end up cutting and rolling the fender lips on all four wheel wells  I ran ten inch wheels with no problems, by the way I still have some rims/tires , if you like Weld Wheels we might do a deal,      Jim Kramer

I have used pump E85 for several years in my Mustang There are advantages and disadvantages , The consistency is a problem, I have a retard set in the MSD box in case I get a poor batch of fuel, but the bigger problem for you would be your intermittent usage of the car, If its gonna sit for more than a week or two you would really need to dump the carb, The alcohol will eventually attack the metal_______Jim Kramer 

Here is a quick drawing of the spacer Now also keep in mind the entire transmission will be pushed back the same distance, mount may take some modding     Jim K

Two pictures show generally what was done, the only thing that really needs to be exact is the opening for the c4 pump size, everything else was done with poster board templets  All done on my little Enco type mill  The COM bellhousing is 850 thousands deeper than the C4 bell, so you have to make a spacer to put into the crankshaft to make up the difference This I made on a friends lathe out of a chunk of round stock, no big deal but it does need to be pretty exact  Kind of a week-end project  Almost no money spent, just some time      Jim Kramer       also- you do have to machine a little off the c4 pump bolt  heads  to fit better into the reliefs cut into the com bellhousing  The com bellhousing is considerably thicker than the c4 so I don't think strength is an issue

i have done it It takes a little fabrication and welding, but not that much and results in a perfectly servicable piece  I used mine in my D/SA mustang for 12 years with no problems____Jim Kramer

I did such a modification on my 390 Mustang race car, ran it for several years with 0 problems     Jim Kramer

Really sorry to hear this   I always enjoyed reading his informative and practical posts  Common sense approach  He was also a good ambassador for Canada  RIP   --Jim Kramer