I’ve recently used the FelPro seal with blue side seals.

Nice kit.

Most of the time it’s the installation that causes the leak, not the seal.

Crank out, make sure the rear retainer is flat where it meets the block. Hand file the two mating surfaces until flat.
Use a light on inside of engine while viewing from rear of engine.

Lay the top seal in the block then the bottom in the retainer.

(Lay the crank in the block and make sure the rear seal lip touchs the crank seal journal).
(Remove the crank).

Install the retainer (mock up) and snug up the bolts then back off one half turn.
See if the retainer moves back and forth - if it does you have to align the lips of the top and bottom seal then snug up the retainer.

Once you have done that - scribe a line from the retainer to the block. This is your reference mark for final assembly.

Remove the seals and retainer - light coat of RTV (light) on back side of seal and install the seal in block.
Do the same thing for the bottom seal.

Install the crank, place a dab of RTV at the bottom of the block in the corner on each side - a light coating on both left and right side of the retainer ends, place the side seals in the retainer grooves so they stick out an 1/8” past the retainer ends. Slide the retainer in to the block - as you get close to being almost all the way in those side seals will become flush with the pan rail.

Align the retainer to that scribed reference point on the block done earlier.

Tighten up the bolts and let it set overnight before running engine.

I have never had a leaking seal using this procedure.

Make sure you don’t use a cracked retainer,