The bombard is the same as a Colossus. They pulled the whole they build them on chimera and leman russ hulls line in the new imperial armour book.
I have 2 bombards that I use as Colossus. You wont get that kit to fit on a chimera mate its just the wrong shape. Just stick a gun on the hull and you are away.
Here is mine so you know what I mean.
Hopefully those shots will show you what I mean by how hard it would be if even its even doable to get that on a chimera. Me and my mate looked into it and just could not see and even remotely simple way of pulling it off.
Also the kit comes with a whole leman russ so you can cut up a sponson heavy flamer or heavy bolter to mount on the hull so its codex correct and it will look fine.
Well I think my heavy flamers look ok anyway
Hope this helps.