Can I bolt a 200R4 behind an LS4 5.3 out of a truck, and is the LS4 the same as an LM7?

The LS4 isn't a truck engine, and it isn't the same as an LM7. LS4 (2005–2009 FWD Impala SS/Monte Carlo SS/Grand Prix GXP) is not recommended for RWD swaps; different bellhousing bolt pattern among other issues.

Engine	Size	Years	Power	Torque	Compression	Block	AFM
LS4	5.3 L	2005–2009	300–303 hp	323 lb-ft	10.00:1	aluminum	Yes
LM7	5.3 L	1999–2007	270–295 hp	315–335 lb-ft	9.49:1	iron	No

If your 5.3 came out of a truck, it's a truck 5.3 (such as an LM7), not an LS4 — check the RPO sticker or the 8th VIN digit (the donor finder lists VIN codes).

200-4R: we don't have a source covering a 200-4R behind an LS, so we can't confirm the adapter details.