66 Plymouth Valiant help!

Hi! I'm brand new here. I pretty much joined because I'm in dire need of some help here.

I have a 1966 Plymouth Valiant Signet. Since it's Canadian, that makes it a 66 Dodge Dart for you folks south of the 49th.

So here's the thing. I'm running a single bowl master with four wheel 9" drums.

I don't want to die.

So I was thinking of installing a dual bowl master, proportioning valve and throwing a set of discs on. However, I have the aggravating 5 on 4 bolt pattern wimpy 7 1/4" rear end.

Changing the front is possible, but then I end up with two different sizes of rims for front and back and then the rear passenger tire has a slow leak so I may as well just change the rear to make everything match!

So I went looking for a new rear end. Up north here outside of Vancouver it's a bit hard to find a 8 1/4" rear end, so I looked for a 8 3/4". I found a 741 highway gear set out of a 74 Charger B-Body($400). Yay or nay?

Next, if it even does fit, I need new rims that can handle what I'm sure will be absurd offset. I really want Smoothies for this ride, so I'm all ears on that subject.

Alternatively, I found a 1988 Dodge Diplomat M-Body 9 1/4" rear end with what the guy calls POSI (THEY DIDN'T HAVE POSI) for $200. Again, with highway gears. Advice?

For the front end, is there any bolt on straight axle deals? Or is that a strictly cut and weld situation? I figure, if I'm going to change the front to handle the new brakes and wheels I may as well go for broke.

There's more, but I think I'll just start with this for now.