66 Advice, Tips, And Knowledge Needed.

So we all have to start somewhere right. I got my first mustang as a gift from my wife 2 years ago and am finally able to get started.
It has-
I6 200, C4 cruise-o-matic, all matching original.
What I'd like to do-
Updated suspension, steering, rear axle, engine/trans, brakes, ect.

So my first questions starts with the danm COM. So when I brought the car home it did ok. After a while it got weaker n weaker. I barley got it on the trailer for our move. N.E.way. I figured the trans needed a lil luvin and did a rebuild, now I have NO engagement what so ever. I used all the new seals/gaskets/clutch packs given (minus a VB gasket cause it did not come in the pack). I was carefull to reassemble it properly but that dnt mean I dnt do something wrong, or that there may be more wrong with it. Now ive been on dozens of threads for info and most get side tracked be for they come up with an answer. So im gana start from scratch.
Please help. Thanks in advance

Hey everyone sry its been so long since I've been on, work/fam/and forgot pw lol. So since my post still haven't been able to get to my car. Did a 420a swap in cuz's Eclipse.
Upgrades that I plan on are.
302 (have 2 complete motors in shed)
Upgrade Cam, Pistons, Carb/Intake, with full rebuild.
Still looking for a T5, any series 83-94
Heidts Mustang 2 IFS kits
Heidts 4-link rear w/built in 9", need info on what 3rd member & axle shafts needed?
Chassis stiffener.
Willwood brake kit.
And paint, seeing as it is factory blue I'd like to stay blue, found an amazing shade from HOC!

Other then that I'd like to just do a RestroMod, Keep it classic with more power and better handling.
Sadly since i haven't done a lot to the car so far, I don't have many pics, unless you count the "garage" roof caving in on it. No damage just scraped the paint lol.

And also need info for rear sump pickup & pan for when I do front suspension kit.