Is this one of the new race chassis with integrated cage? it looks like the rear frame is elevated on either side of the differential and it mounts differently than what i've seen before with the S3 frame configuration. Was this a customization for your setup or did the frame design change? It also looks like the older style nosecone? I preferred it's configuration vs. the new style to accommodate frame changes.
I can't speak to your choice of engines but hope this comes together without too much fiddling and faffing about.
Another potential resource for you is here:
https://usa7s.net/ips/best of luck.