Who says the (Reformed) gospel is antinomian? Here we have the Reformed of the Reformed speaking on Hebrews 12:14, i.e. "Strive for peace with everyone, and for the holiness without which no one will see the Lord." (ESV). You don't have to become a papist or federal revisionist to preach holiness.
[the] future sight of the Lord doth depend peremptorily on our present holiness. It doth not do so as the meritorious cause of it; for be we never so holy, yet in respect of God we are "uprofitable servants," and "eternal life is the gift of God by Jesus Christ." But it doth so on a double account: (1.) Of an eternal, unchangeable, divine constitution. God hath enacted it, as an eternal law, that holiness shall be the way of our attaining and coming to blessedness. (2.) As it is a due preparation for it, the soul being by holiness made meet and fit to come to the sight of the Lord, Col. 1:12, 13. And therefore... in whom this holiness is not, he shall never see the Lord. And -
Obs. II. They are much mistaken in the Lord Christ, who hope to see him hereafter in glory, and live and die here in an unholy state. It is not privileges, nor gifts, nor church office or power, that will given an admission to this state.
Obs. III If this doctrine be true, that "without holiness no man shall see the Lord," the case will be hard at last with a multitude of popes, cardinals, and prelates, who pretend that they have the opening of the door into his presence committed unto them.
(John Owen, Hebrews Volume 7 Banner of Truth)