No amount of force will get these fulcrum bolts out if you wont know how. Turning them is not possible on a rear end like yours the way you've been trying to. There is a video I've posted here a while ago on howto get them out but I cant find it right now, but the idea is you take both wishbones off the car with the diff bracket still attached and both bolts passing through it and the wishbones, you put it all on the floor and either have another couple people standing on one wishbone and an extension and a socket securing the fulcrum bolt to the floor while you lift up the other wishbone off the floor to crack the rust and turn it. That way you have waaaaay more leverage as you're not turning the bolt but a huge wishbone around it.
The moment you crack it loose within the wishbone you'll be able to move it up and down fairly quickly and that will allow you to get a wire brush on a grinder around middle section to clean up all the rust and eventually it will come out, then repeat on the other side. The only other method is to cut it out and then hammer it out in 3 pieces but then you're paying for replacement and they aren't exactly cheap.
This could also be done with the rear end attached firmly to the car and diff supported and car on the lift but its more fiddly that way.
Lower shock bolts are a pain too but these are cheap to replace and if they seize to the shock bush I normally just cut them off and replace. You'd need a press to get them out if they seize for good, I've beaten on some to a point where I've completely mushroomed them and they still didn't want to come out as the bush basically dampens your hammer. Easier to replace with these.
Hope this helps!
.

 

I have the X308 differential strut / crossmember on a piece of white foam with a ruler to photograph but can't get the laptop to take a picture

used it last week

 

Wow. Those large wishbone pivot bolts(#2) are quite pricey for what they are. Over $200 each new in the US? Seems.......excessive. I wonder if there was/is anything special about that bolt(like material, hardness, shaft od) that can be found elsewhere for a better price without the Jaguar expense, I mean branding, on it? I'd like to find a drawing with some dimensions on it for that bolt. Maybe some eBay shopping is in my future?

 

Also, after looking at these more, I think I will be adding a lower brace(something that I'll fabricate) that connects the front and rear cast supports. Were the lower crossmembers there more for the rear suspension flexing or to help keep the back of the car more rigid?

And thank you all for the help, it's awesome!

 

Got a pic and looking for it to add dimensions

The bolts at the salvage yard can be obtained if the car is put on a rack with the suspension hanging

That's how I extracted the X308 differential strut and extra fulcrum bolts

 

First pic so let me put some scale and orientation references in

 

Want a pic from a different angle ?

Your request

 

Hi Parker,

That picture does me wonders! Thanks! I appreciate all the help! I should be able to sneak a bar through there without much issues I think. I'll have to measure. If a stock one fits, it'll save some work for sure. Not afraid of it, but as you can see from the overall picture, I have plenty to do.

Sadly, here in the New England area, I'm afraid a salvage yard trip won't be too fruitful due to all the salt put on the roads. I think the extraction of the wishbone pivot bolts will be for another day. After seeing their cost, I'll keep building with what I have and will source those when I put it together for good. I have some bushings that will keep it all centered in the mounting bushings so there isn't a ton of bolt slop.

I'll also have to start looking for some upgrade parts for it too. Not a fan of the one wheeler peelers. Any other tips/tricks/things to look for?

Thanks,
Matt

 

So the bow out is right in line with your upper mount bolts , the bow out is pointing up in this angle which is worst case scenario depending on your standoffs on your present frame pic

 

See video on how to remove fulcrum bolts.

https://photos.app.goo.gl/7RMad4A1ywvPMGVC9

The whole idea is to crack it loose first by turning the wishbone, not the bolt. Video starts when I've already cracked it loose, lifting it up off the ground first time is not easy to say the least but its definitely the only way to do it.

They are Jaguar special bolts, designed to not snap but bend even on great impact, hence the price, you do not want to replace them with cheaper alternatives as rear end wouldn't be safe.

 

The last pic could be better from a different angle but got to run after some dinner fixings

 

+ 1 vote for everything he said especially the fulcrum bolt strength

The last thing you want is for a suspension bolt breaking driving your car in a unwanted direction

I used to keep a bolt from a 747 aircraft flap that was getting ready to shear off hence the TSB being performed , it was wildly deformed and not sheared or snapped so it had some ductility

 

https://www.ebay.com/itm/23467842206...mis&media=COPY

i have several extra pivot bolts. or buy off these guys