I should have asked what you are starting with; a passive radiation shield, a daytime fan aspirated radiation shield (DFARS), or a factory supplied 24 Hr fan aspirated radiation shield (24Hr FARS). If you are starting with anything other than a factory supplied 24 Hr FARS then I don't think you would have a welded core unless you ordered one. It looks like the DFARS to 24Hr FARS gets you part way to the factory supplied 24Hr FARS but not the entire way. It seems like the kit omits the welded core and the associated parts that would require the welded core. Without the welded core, the insulated sleeve p/n 7342.508 will have no where to sit. The screen p/n 7345.023 will also have no where to go since it attaches to the bottom of the welded core. Please note that the picture of the welded core in the previous link is upside down. The picture has the core sitting on it's top where the fan and the batteries are mounted. The presence of the welded core is not clear in the linked 24HR FARS exploded view because the lower tube is obscured by the caps p/n 7342.236. I started with a factory supplied 24HR FARS so I haven't attempted any conversions.
