LSx Valiant Build. Take a look inside...
I see you ran into the very reason I wuit the ls build on my car. Upside down manifolds was all I could run or custom headers etc... the cost was over welming for me to stick with it all. Insold all my ls stuff at a profit and went newgen hemi. My plans was always 1200+rwhp turbocharged. So I had no intentions to keep a stock ls short block. Currently the newgen hemi is a better deal now than an ls swap parts for parts if your after big power and reliability. If your staying in the relm of under 800hp ls will work fine but not without exhaust being custom or upside down.
Fwiw a stock oil pan from a gto fit perfectly on my setup. So did the proflo under my stock hood. I think the holley ram would clear as well as I had inches left still above the proflo.
Below was my blasphemous build I got shunned on as well. Anothe forum made it over 100 pages of mopar purists cried foul....many from this very site. Lol. Love the idea but hate the fab work. Ill be watching to see if you stick with it or change direction as I did.