454/TH400 install questions

[earl84]

I have done some research on here about the engine perches, and I think what I have figured out is that the current perches I have in my 66 C20 that held a SBC 350 will work for the 454, but will have to be moved to the forward set of holes. Is this correct?
Also, I pulled out the engine and SM420 yesterday, and from what I understand, the SM420 trans crossmember will have to be removed and a different crossmember installed further back. Is this correct?
I will figure out the placement of the crossmember when I have taken delivery of the engine and transmission. Can my SM420 crossmember be modified to work easily or is it just too much hassle? I am currently without a welder, but looking to purchase one before too long.
One last question on tips of how to remove the SM420 crossmember. It looks like I can get to the lower rivets easily enough, but the uppers may be an issue. The cab is still on the truck. Planning on a grinder and serious hammer blows to get the rivets out, and drilling if necessary. Any hints?

[64swb]

I put a 396 and th400 in my old '63 years ago. Used the forward set of mounting holes for the motor mounts and a short water pump accessory drive setup. I had hardly any clearance between the firewall and the valve covers with stock height valve covers. My truck had a powerglide so no 4 speed cross member to deal with. I have seen guys just cut the off flush with the edge of the frame with a swazall. It looks like s**t but its easy. For the trans cross member I used one from a 70s suburban.

[Rich 5150 69]

Trans crossmember is not a problem, get any crossmember from an auto, `73 to `87 truck or suburban, remove yours and bolt in the donor where needed.

[Captainfab]

The motor mount brackets from the rear location will not bolt up correctly in the forward location. For the forward location you need the brackets for a '67-'72 with a small block. Those are designed to bolt into the forward location. Or if you wanted to go in between those locations, get yourself a set of the '68-'71 big block brackets and mounts. Alternately you could go with the better '73+ motor mounts, but you will want the motor mount brackets from a '73-'87 C20 or 30.

For a trans crossmember you just need an auto trans crossmember from a '63-'87 truck or Suburban. You'll just have to drill the bolt holes.

[earl84]

Thanks for the replies. I will have to start doing some looking. RockAuto has some dirt cheap motor mounts, so I think I will replace those as well. Wish they had the perches and crossmember, it sure would make it easier. Think I'll go with the 73+ BB perches, and I may have to do the butt ugly Sawzall method on the crossmember if I can't get the rivets out of the old manual crossmember.

[Chevy Fleetside]

If you remove/drill out the bottom rivits you might be able to get a longer drill bit and drill out the upper by going through the lower holes. I put a BBC in one of my 65's. I used tubular engine mounts that I got from Truck and car shop but I also cut the firewall for valve cover clearance so I could use the rear holes. I had to trim the upper frame rails for the new perches but you have to do that with the later model ones also. My thread is in my sig.