Need help from Guys with Stock Frame ADs with LS

[Root2812]

I'm about to drop my 5.3 into my 1950 truck, or should I say bare frame. I know that I don't want to recess the firewall and if I had a cab on my frame I'd install my engine based on the firewall but sadly I don't have a cab on it. My truck is still fully assembled and I drive it, I'm building a new chassis to do a body swap to next winter. I have a kid coming in just a few months and I really want to get the engine running in the frame before my daughter comes. I'm hoping you guys can help me out with 2 things.

So I have a stock frame, don't want to cut the firewall, and have a 5.3 LS with truck accessories. I've seen pics of them in there and its tight so I got the Dirty Dingo slider mounts (link below) for that adjustability after the body is on. Can any of you guys who have been successful give me some measurements so I can get close? I don't have a radiator but something like radiator support to waterpump pulley would be a great measurement. Anything you think may help me get in the ball park. There is a pic below of what I have right now. I do have the radiator support but its not on in the picture. Those mounts have 3 inches adjustability (I'll go in the middle so 1.5 each way) so I just need to be within an inch or so.

http://dirtydingo.com/store/index.ph...=1_206_305_321



So my second hold up is the fuel tank issue. I'd like to see what guys running the stock frame with LS engine are using. I have the TCI leaf kit so there will be lots of room after the spare tire cross member comes out. I know people use nearly every tank under the sun but I'd like to see the ones with the LS pumps to get ideas. Do I need a baffled tank?

Thanks a lot guys. This is my first build and I'm trying to read a ton to figure it all out but this is the time I think I need help most. I'll be glad to share lots of pics and a video when it runs.