Ok...rethinking how to use $6k

Ok, those of you that read my first post found I was focused solely on whether to rebuild my 318 or go to a 360. After reading the feedback I've since rethought my strategy on how to deploy the $6k I have to use this year for my 68 Dart GT. After more thought I feel if I start out upgrading brakes and rear end--and doing wheels and tires to get the stance and look--I'll be much better positioned once I figure out the engine/transmission later. Right now I'm looking at a complete rear assembly(8.75, tru trac, 3.55 gears) that will get me to 5 x 4.5 bbp including rear disc brakes for about $3250. Then I'll use the rest on a front disc brake kit, new master cylinder, and wheels and tires. Right now I'm looking at 225/45/17 in front and 245/40/18 in back. I know they're expensive, but I like Coy wheels and have been looking at those. I'm a newb so any thoughts on this plan are greatly appreciated!