[ABLAZN]

I have a 454 in my Blazer (installed from the PO) and it rubs the firewall fairly tight. So firewall clearance is an issue. Also the turbo 400 is not going to work without getting a turbo 400 specific adapter and 205 transfer case. If you can find one they are usually expensive . You could always go with a turbo 400 adapter/208 transfer case combo from a newer GM, but then you would need to change your drive line ends. So in other words, you can do it, but it is not just a simple conversion.