Its a hard question as I believe 10.5 ET in a full dressed E that is also "steetable" takes a well built BB stroker. Not a budget option. Your signature car is probably quite a bit lighter than a dressed E... and runs real well.

Comparing a "well built" 400" SB and a "simple" 440 I guess the ET would be similar but the BB would be more fun on the street with more torque and a better match to 3.55 gears. ET I won't guess but probably more than 10.5 for both.