X18 motor advice

[72x2]

I am trying to get information on x dimension for an X18. I have found a deal on a 502 with a bravo 1. It seems that this is about 164lbs heaver than a 350 mag with a bravo 1. I have heard that there were a few big block trs drive boats made. I would think that that set up would weight more than the 502 with bravo.
I am trying to decide if the 502 would be a good way to go and how high the x dimension should be.
I am adding a 41 gallon gas tank in the current location with minor modification to the rear bulkhead.
Any input or information would be appreciated.
Thanks

[pipnit]

Hey There,

I have a 76 2+3 with a small block and a TRS. Don't forget the TRS boats have the velvet drive transmission which weighs something too. I now have aluminum heads and some headers so I've lightened it up a good but but I wouldn't be surprised if stock, my setup was heavier than what you're thinking about doing. I guess I also added some weight with the hydraulic steering though.
I hope this helps!

IMG_A8ADF5BF-7DE7-4E7D-B555-966B86CAF58E_lg.jpg

[gcarter]

Don't forget that the BBC engines are so much larger, and thus harder to work on w/less room around the engine.
18's respond well to potent SBC's and many run well into the 80's.