Like Mudder67 said, you should be fine on your driveshaft lengths. You will definitely need longer shocks or you will reach the extension limits under articulation. You should also get longer front brake hoses. The rear should be long enough for 3 or 4 inches of lift. I also wouldn't re-arch the front springs. I think new front springs can be purchased for around $300, maybe a little more.
I put an 8" suspension lift on my 67 (same as 68) so if you have any further questions, don't hesitate to email me or send me a private message.
Rob Pont
pont1@rvi.net