Upgrading a 68 Camaro

[Astontibs]

I want to introduce myself to the forum. My name is Alan Tibbetts and I have owned my 68 Camaro since 1985. I have done all the standard restification stuff on it and I am now ready to begin some bigger mods like subframe replacement, aftermarket AC and LS engine transplant. First on the list is the subframe replacement and in researching my options I came upon your forum. I look forward to all the help you can give me. here are some current specs on the car.
355 CI small block about 400 crank horsepower
Tremec TKO600
3.73:1 12 bolt posi
Front and rear disc brakes (Chevelle front, GM retrofit Cad Seville rear)
Poly bushings throughout
17X8, 17X9 Foose Legend wheels with 225-50-17 and 275-50-17 tires.
Lakewood traction bars on multileafs
Bolt in subframe connectors
1" front swaybar

I attached a picture of the car, but it is before I had the Chip Foose wheels.