Putting an XR5 360 in the front does open up some options compared to the 420mm radiator - there's more space on the side. If, that is, you mount the radiators in the offset position, rather than on the centerline.
With an XD7 In the side
One option for the side would be the XD7 Distribution Plate/Pump/Reservoir but there are a couple of challenges (though easily enough overcome).
The radiator inlet and outlet ports are pretty close to the radiator (shown in the insets). That said, a 90 degree fitting will work. But you will need to account for this when planning your loop.
If you want to configure your radiator as push/pull, you'll either need to leave off a fan or mount the radiator and XD7 in offset positions (as shown in the image on the right). This is due to the bulge from the pump covering the radiator where the inside fan would go. However, in the offset position, you won't be able to use a 420mm radiator in the top.
When using the XR5 360 in the front, there is plenty of room for push/pull with either the standard PSU shroud cover or with the low profile PSU shroud cover. With the radiator in the lowest position, you won't be able to use the first HDD cage either.
With an XR5 in the side
Another option is to put a third radiator in the side - another XR5. You can put up to an XR5 360 in there; the XR7 won't fit in the side with a radiator in the front. There is room for push/pull on the front radiator but the side radiator can only have one set of fans. It may also be possible to directly connect one radiator to another at the bottom.
Top Mounting Considerations
The 360mm radiator fits easily with any radiator in the top. However, if you have a 420mm radiator in the top, you are limited in the positioning of the radiator and fans - they have to be mounted lower rather than at the top due to the length of the top radiator; there just isn't enough space for both of them there. That would also go for any 3rd party 30mm deep 480mm radiators. You can, however, use any 120mm class radiator in the top, including the XR7 360 (as shown in the images).
With an XR7 360 in the top, you have a little over 30mm of clearance between the front XR5 and the front of the XR7 in the top if you are only using push OR pull (1 set of fans). This gives you enough room for push/pull on all fan positions in the front. If you want to do push/pull with an XR7, it's gets a little more challenging as you need to move the radiator forward so that you have clearance with your motherboard I/O shield. This reduces the clearance - with the ports in the front - to just 18mm. That's not enough for push/pull in the front or an XR7 480mm. Installing the front XR5 into a lower position will eliminate this challenge - but then you'll be blocked by the pump on the XD7.