you might test-fit those SLP headers on a spare engine
before beginning the install,i bought two pairs of those
back in the 90s,and though they were of very good
design and materials(nice forged S.S. flanges etc

)
,they has rather bad assembly quality

-ist set bought
in '96 had flanges that weren't welded on straight
(double stacked exhaust gaskets and got it to seal)also
y-pipe wasn't straight,had to tweak a bit.in 1998, i
reconed they must have fixed the quality problems after
2yrs, so decided to try another set: this set was worse!

-unusable without extensive rework-reamed summit
and sent them back(they said i had bad engine mount
etc.

)tried eldebrock-those were great quality and
fit really nice (still good today,no problems) the SLPs
made more power,so i might rework and reinstall those
someday