Helgaker, Jaszunski, and Swider^{1} have examined the use of B3LYP with four different basis sets to compute the spinspin coupling constants in strychnine 1.

They used previously optimized coordinates of the two major conformations of strychnine, shown in Figure 1.
Conformer A 
Conformer B 
Figure 1. Confrmations of strychnine 1.
They tested four basis sets designed for NMR computations: pcJ0,^{2} pcJ1,^{2} 631GJ,^{3} and 6311GJ.^{3} pCJ0 and 631GJ are relatively small basis sets, while the other two are considerably larger.
All four basis sets provide values of the 122 J(CH) with a root mean square deviation of less than 0.6 Hz. J(HH) and J(CC) coupling constants are also well predicted, especially with the larger pcJ1 basis set. They also examined the four Ramsey terms in the coupling model. The Fermi contact term dominates, and if the large pcJ1 basis set is used to calculate it, and the smaller pcJ0 basis set is used for the other three terms, the RMS error only increases from 0.18 to 0.20 Hz. Taking this to the extreme, they omitted calculating any of the nonFermi contact terms, with again only small increases in the RMS – even with the small pcJ0 basis set. Considering the computational costs, one should seriously consider whether the nonFermi contact terms and a small basis set might be satisfactory for your own problem(s) at hand.
References
1) Helgaker, T.; Jaszuński, M.; Świder, P., "Calculation of NMR Spin–Spin Coupling Constants in Strychnine." J. Org. Chem. 2016, ASAP, DOI: 10.1021/acs.joc.6b02157.
2) Jensen, F., "The Basis Set Convergence of Spin−Spin Coupling Constants Calculated by Density Functional Methods." J. Chem. Theor. Comput. 2006, 2, 13601369, DOI: 10.1021/ct600166u.
3) Kjær, H.; Sauer, S. P. A., "Pople Style Basis Sets for the Calculation of NMR Spin–Spin Coupling Constants: the 631GJ and 6311GJ Basis Sets." J. Chem. Theor. Comput. 2011, 7, 40704076, DOI: 10.1021/ct200546q.
InChIs
Strychnine 1: InChI=1S/C21H22N2O2/c24181016191391721(6722(17)1112(13)582516)14312415(14)23(18)20(19)21/h15,13,1617,1920H,611H2/t13,16,17,19,20,21+/m0/s1
InChIKey=QMGVPVSNSZLJIAFVWCLLPLSAN