47-55.1 Help locating a 5.3 in '51 3600

[51 3600]

Been on this great forum for awhile but mostly looking, reading and learning. Now I'm at a point where I'm going to an outside shop to do work I have neither the skills nor equipment to do. They have skills and equipment but my project is not the norm for them so I'm seeking info to help in the process.

Objective is to install a LM7 5.3 engine from a '01 Tahoe along with 4L60e trans and 8.8 Exploder rear end with Jeep Wrangler leaf springs into my '51 3600 frame. Front suspension already installed is a Danforth crossmember with '01 Blazer suspension.

First task is installing engine mounts so I need help with proper positioning/locating engine and trans. I've seen a lot of pics here but can't find info as to where exactly that engine should sit (Pics attached show where engine is presently planned to sit). So my questions are:
1) Knowing engine bay is cramped in length, how far back can/should the engine sit in relation to radiator crossmember assuming use of electric fan?
2)Will fire wall have to be modified (tunnel) to accept trans?
3) How low can the engine sit, if possible, to avoid #2 above?
4) Does the original oil pan have to be replaced with another unit?
5) Other questions you know I should be asking but am too ignorant to do so.

Trying to keep ride height of truck close to original because I want to use it in my work so no lowering, no air ride, etc. Upgrading drivetrain so more practical on highway.

Thanks in advance for any info. Oh, I'm no mechanic so simple not too technical explanations would be appreciated.