400b help please

I'm not knowledgeable but I'm trying here goes I have a 73 400 block it's supposed to be a 451 I had the pan off wish I would have taken more photos! It looks to me the crank shaft has been machined as you can see in the photos looks like stock rods ? .. the problem is the balancer is for a external balance 400 see photo as example.. I hope I'm wrong but seems to me it's a 451 built with a cut cast crank instead of 440 steel crank .. and is not a good thing to do ..if anyone can tell me anything at all from these photos it will help me what do you guys think I was told a cast crank has a thin line on it from being cast and a steel crank has a fatter line from being forged ? .. it does run good and makes decent power it will spank my 70GS455 Buick thanks