This does what you asked for but not, I think, what you meant:
[{"id":"12ee2679.01330a","type":"inject","z":"586832c7.9dc7fc","name":"","topic":"","payload":"","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":250,"y":1740,"wires":[["6d4603bd.67f33c"]]},{"id":"6d4603bd.67f33c","type":"function","z":"586832c7.9dc7fc","name":"","func":"msg.payload = {\n input: [17354, 784],\n}\n\nmsg.payload.output = `0x${msg.payload.input[0].toString(16)}${msg.payload.input[1].toString(16)}`\n\n\nreturn msg;","outputs":1,"noerr":0,"x":390,"y":1740,"wires":[["d73f8f6e.e183c"]]},{"id":"d73f8f6e.e183c","type":"debug","z":"586832c7.9dc7fc","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":610,"y":1740,"wires":[]}]
The reason I think it is wrong is that the output with the given input is not the expected 32bit output. Though I may be making more assumptions than warranted.
You probably need to use padStart
with a leading zeros to make each string 4 characters long?
The result as written gives a value of 71,082,768 (0x43CA310), whereas you may want 1,137,312,528‬ (0x43CA0310)?