Front Disc Conversion and all 5 lug conversion

[chiggins]

I have a 1968 Chevy and I want to convert the front brakes to power disc and converting both front and rear to 5-lug. I am on a very tight budget and trying to find the cheapest options. I have heard rumor that the front sub-frame (whole steering assembly and brake system) of a square body Chevy (73-87) will bolt right in with little modification. I just want confirmation from a good source if that is true before I go and buy a donor truck.
And as for the rear axle conversion. I believe its true that the trucks switched to being 5-lug around 70-71. So could I take the rear axle of one and bolt it right into mine?
I also need some build tips on what to use for bucket seats. I'm hoping I can use seats out of a 2003-ish Suburban/Tahoe because they have the seatbelt assembly built in. But I'm afraid that they may be to big. I'm going to relocate the gas tank to under the bed, which would give me more room.

Any suggestions would be greatly appreciated. This is my first truck, so I am completely new to this.