I figured out how he did the back of the system. He used an open rack used for bitcoin rigs for the rear of the system. Or he is a whiz with a metal cutter.

https://www.amazon.com/ALAMENGDA-Computer-Motherboards-Dissipation-Accessories/dp/B0C59W6JKD/ref=sr_1_2?crid=1J6A7NSXCLB94&dib=eyJ2IjoiMSJ9.-h_hgl00x9RGqV0HTZ3-V2h560uZc2OhITSYUZJu_qP4Hszgp_htzZHY2fCFILb4T4W7B6KzaJICngPjTJ4gJSErkEfQIkt04MFXNBxNvDUg4u4f4MFUyQDEvxYFdU2jk6-cIOezzLaxLqtlOcwzPrj-2D-_FNlEtr4sY_msLOnsfI8U12KPjRXc1i-WYhhHtI6zENcXHYhZfutPXC-kA7bUBFF8Tf87362cdXg2IhuJ0_lDb4Ga1TEI3PKYG1gz7kwfwgTdgPGNBBX3FBgZfrV2YROSdLueRSaCTAEWbjM.9Y1q9BDCJn72LXXHJtxw-rf26nrxJ0UHOR3Qgd4rCco&dib_tag=se&keywords=open+motherboard+case&qid=1709685013&s=electronics&sprefix=open+mother%2Celectronics%2C166&sr=1-2

I also found this: https://www.youtube.com/watch?v=2lLoO5tI5cQ&t=189s

Old video but he did a total custom job and built a 5150 replica case out of MFA and cut the metal parts from another case. I question if I could put a monitor on top full time.

That is correct, the 5150 used a completely proprietary layout because there wasn't any real spec or guidelines at the time. The XT was similarly slightly different even though the cases looked the same.

The pictures are of an XT case, make sure you're getting the one you need.

I will say the PC and XT had absolutely miserable airflow to the point of machine-killing - even for those old 8088 CPUs. When you get an XT case, pull the cover off - there's probably black tape across some ventilation holes on the front. That was an attempt by IBM to correct the terrible airflow in those cases. Just something to keep in mind because today's stuff generates a lot more heat.