How many tools and how much equipment do you have? This is a major undertaking as if done right NONE of the drive train, steering, or suspension will be retained. We have done at least a dozen BB into AD's but I usually try to steer the customer towards a 427 or 502 since the 454 was designed by GM to be a smog (lower emissions) engine. All are physically the same size on the outside. If some of the speed equipment you have ordered includes aluminum heads and intake the weight factor gets way better. If you must have a manual transmission then you need to find a 60-62 V8 bell housing that uses the passenger side hydraulic clutch release. This unclutters the left side which already has the pedals and maybe the shift rods for additional exhaust room. By far the best is to go with an automatic (PG for least intrusion to 700R4 for most) as this leaves both sides wide open for exhaust. A frame clip from a BB Chevelle would include everything needed for steering and suspension as would a MII DESIGNED for a BB like say from Fatman---not cheap. An open driveshaft rear end in the 3.00 to 3.25 ratio and with triangulated 4 link and disc brakes all around will provide the needed go and whoa. I have seen AD's with BB's that retained much of the original design and can usually find who owned them by watching the obituaries. Pics are of a 54 3100 that is all set up for BB clearance but has an LS with coil covers that bring the dimensions close to that of a BB.
Note recessed firewall:
[img]https://i.postimg.cc/cg1wPNXc/IMG-4837.jpg[/img]Recessed firewall inside view; under dash panel is for a/c vents:
[img]https://i.postimg.cc/yg5xnq5x/IMG-4839.jpg[/img]Rear end set up that will take the torque of a BB:
[img]https://i.postimg.cc/4HfGzW4y/IMG-4840.jpg[/img]
