Are all 5.3 blocks the same?

No. GM built 16 different 5.3 L engines across three generations. They share a 3.78 in bore and 3.622 in stroke, but differ in block material, AFM, VVT and injection:

Engine	Family	Years	Block	AFM	VVT	DI
LM7	Generation III	1999–2007	iron	no	no	no
L59	Generation III	2002–2007	iron	no	no	no
LM4	Generation III	2003–2005	aluminum	no	no	no
L33	Generation III	2005–2007	aluminum	no	no	no
LH6	Generation IV	2005–2009	aluminum	yes	some years	no
LS4	Generation IV	2005–2009	aluminum	yes	no	no
LY5	Generation IV	2007–2009	iron	yes	some years	no
LC9	Generation IV	2007–2014	aluminum	yes	some years	no
LMG	Generation IV	2007–2014	iron	yes	some years	no
LH8	Generation IV	2008–2009	aluminum	no	no	no
LMF	Generation IV	2008–2014	iron	no	some years	no
LH9	Generation IV	2010–2012	aluminum	no	yes	no
L83	Generation V	2014–2020	aluminum	yes	yes	yes
L8B	Generation V	2016–2018	aluminum	yes	yes	yes
L84	Generation V	2019-2026	aluminum	yes	yes	yes
L82	Generation V	2019–2021	aluminum	yes	yes	yes

"Some years" means only certain model years had that feature (the source table marks these). The LS4 is listed as a front-wheel-drive (FWD) application. Gen V 5.3s (L83, L82, L84, L8B) are direct-injected LT-family engines, so check that any swap parts and engine controller you pick support Gen V.

Find yours in the donor finder.

Specs are GM ratings as published; power varied by year and vehicle. Confirm any engine by the RPO code on the glovebox/console sticker.